2024-04-28 18:19:41 -05:00
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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"/><meta name="viewport" content="width=device-width, initial-scale=1"/><title> <loganGatlin/> </title><link type="image/x-icon" rel="icon" href="resources/favicon.svg"/><style>
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2024-04-28 17:11:48 -05:00
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/*!
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Pure v3.0.0
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Copyright 2013 Yahoo!
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Licensed under the BSD License.
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https://github.com/pure-css/pure/blob/master/LICENSE
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*/
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/*!
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normalize.css v | MIT License | https://necolas.github.io/normalize.css/
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Copyright (c) Nicolas Gallagher and Jonathan Neal
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*/
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/*! normalize.css v8.0.1 | MIT License | github.com/necolas/normalize.css */html{line-height:1.15;-webkit-text-size-adjust:100%}body{margin:0}main{display:block}h1{font-size:2em;margin:.67em 0}hr{box-sizing:content-box;height:0;overflow:visible}pre{font-family:monospace,monospace;font-size:1em}a{background-color:transparent}abbr[title]{border-bottom:none;text-decoration:underline;-webkit-text-decoration:underline dotted;text-decoration:underline dotted}b,strong{font-weight:bolder}code,kbd,samp{font-family:monospace,monospace;font-size:1em}small{font-size:80%}sub,sup{font-size:75%;line-height:0;position:relative;vertical-align:baseline}sub{bottom:-.25em}sup{top:-.5em}img{border-style:none}button,input,optgroup,select,textarea{font-family:inherit;font-size:100%;line-height:1.15;margin:0}button,input{overflow:visible}button,select{text-transform:none}[type=button],[type=reset],[type=submit],button{-webkit-appearance:button}[type=button]::-moz-focus-inner,[type=reset]::-moz-focus-inner,[type=submit]::-moz-focus-inner,button::-moz-focus-inner{border-style:none;padding:0}[type=button]:-moz-focusring,[type=reset]:-moz-focusring,[type=submit]:-moz-focusring,button:-moz-focusring{outline:1px dotted ButtonText}fieldset{padding:.35em .75em .625em}legend{box-sizing:border-box;color:inherit;display:table;max-width:100%;padding:0;white-space:normal}progress{vertical-align:baseline}textarea{overflow:auto}[type=checkbox],[type=radio]{box-sizing:border-box;padding:0}[type=number]::-webkit-inner-spin-button,[type=number]::-webkit-outer-spin-button{height:auto}[type=search]{-webkit-appearance:textfield;outline-offset:-2px}[type=search]::-webkit-search-decoration{-webkit-appearance:none}::-webkit-file-upload-button{-webkit-appearance:button;font:inherit}details{display:block}summary{display:list-item}template{display:none}[hidden]{display:none}html{font-family:sans-serif}.hidden,[hidden]{display:none!important}.pure-img{max-width:100%;height:auto;display:block}.pure-g{display:flex;flex-flow:row wrap;align-content:flex-start}.pure-u{display:inline-block;vertical-align:top}.pure-u-1,.pure-u-1-1,.pure-u-1-12,.pure-u-1-2,.pure-u-1-24,.pure-u-1-3,.pure-u-1-4,.pure-u-1-5,.pure-u-1-6,.pure-u-1-8,.pure-u-10-24,.pure-u-11-12,.pure-u-11-24,.pure-u-12-24,.pure-u-13-24,.pure-u-14-24,.pure-u-15-24,.pure-u-16-24,.pure-u-17-24,.pure-u-18-24,.pure-u-19-24,.pure-u-2-24,.pure-u-2-3,.pure-u-2-5,.pure-u-20-24,.pure-u-21-24,.pure-u-22-24,.pure-u-23-24,.pure-u-24-24,.pure-u-3-24,.pure-u-3-4,.pure-u-3-5,.pure-u-3-8,.pure-u-4-24,.pure-u-4-5,.pure-u-5-12,.pure-u-5-24,.pure-u-5-5,.pure-u-5-6,.pure-u-5-8,.pure-u-6-24,.pure-u-7-12,.pure-u-7-24,.pure-u-7-8,.pure-u-8-24,.pure-u-9-24{display:inline-block;letter-spacing:normal;word-spacing:normal;vertical-align:top;text-rendering:auto}.pure-u-1-24{width:4.1667%}.pure-u-1-12,.pure-u-2-24{width:8.3333%}.pure-u-1-8,.pure-u-3-24{width:12.5%}.pure-u-1-6,.pure-u-4-24{width:16.6667%}.pure-u-1-5{width:20%}.pure-u-5-24{width:20.8333%}.pure-u-1-4,.pure-u-6-24{width:25%}.pure-u-7-24{width:29.1667%}.pure-u-1-3,.pure-u-8-24{width:33.3333%}.pure-u-3-8,.pure-u-9-24{width:37.5%}.pure-u-2-5{width:40%}.pure-u-10-24,.pure-u-5-12{width:41.6667%}.pure-u-11-24{width:45.8333%}.pure-u-1-2,.pure-u-12-24{width:50%}.pure-u-13-24{width:54.1667%}.pure-u-14-24,.pure-u-7-12{width:58.3333%}.pure-u-3-5{width:60%}.pure-u-15-24,.pure-u-5-8{width:62.5%}.pure-u-16-24,.pure-u-2-3{width:66.6667%}.pure-u-17-24{width:70.8333%}.pure-u-18-24,.pure-u-3-4{width:75%}.pure-u-19-24{width:79.1667%}.pure-u-4-5{width:80%}.pure-u-20-24,.pure-u-5-6{width:83.3333%}.pure-u-21-24,.pure-u-7-8{width:87.5%}.pure-u-11-12,.pure-u-22-24{width:91.6667%}.pure-u-23-24{width:95.8333%}.pure-u-1,.pure-u-1-1,.pure-u-24-24,.pure-u-5-5{width:100%}.pure-button{display:inline-block;line-height:normal;white-space:nowrap;vertical-align:middle;text-align:center;cursor:pointer;-webkit-user-drag:none;-webkit-user-select:none;user-select:none;box-sizing:border-box}.pure-button::-moz-focus-inner{padding:0;border:0}.pure-button-group{letter-spacing:-.31em;text-rendering:optimizespeed}.opera-only :-o-
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</style><style>
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@font-face {
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font-family: Cascadia;
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src: url("/resources/CascadiaMonoPL.woff2");
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}
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body {
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color: #444;
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font-size: 1.2em;
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}
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.link {
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text-decoration: none;
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color: #1e90ff;
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}
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.link :visited {
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color: #1e90ff;
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}
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table {
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display: block;
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margin-top: 1em;
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margin-bottom: 1em;
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margin-left: auto;
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margin-right: auto;
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width: 60%;
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text-align: left;
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border-collapse: collapse;
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}
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th {
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padding: 0.25em 0.25em 0.25em 0.25em;
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border: 2px solid;
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border-collapse: collapse;
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}
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td {
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padding: 0.25em 0.25em 0.25em 0.25em;
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border: 2px solid;
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border-collapse: collapse;
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}
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/* https://css-loaders.com/spinner/ */
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/* HTML: <div class="loader"></div> */
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.loading {
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width: 512px;
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padding: 8px;
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aspect-ratio: 1;
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border-radius: 50%;
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background: #25b09b;
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--_m:
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conic-gradient(#0000 10%,#000),
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linear-gradient(#000 0 0) content-box;
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-webkit-mask: var(--_m);
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mask: var(--_m);
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-webkit-mask-composite: source-out;
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mask-composite: subtract;
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animation: l3 1s infinite linear;
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}
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@keyframes l3 {to{transform: rotate(1turn)}}
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.centered {
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display: block;
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margin-top: 1em;
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margin-bottom: 1em;
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margin-left: auto;
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margin-right: auto;
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justify-content: center;
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width: 50%;
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}
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.pure-img-responsive { max-width: 100%; height: auto;
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}
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.cascadia {
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font-family: Cascadia;
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}
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.home-menu {
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padding: 0.5em;
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text-align: center;
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box-shadow: 0 1px 1px rgba(0,0,0, 0.10);
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}
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.home-menu {
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background: #333;
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}
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.home-menu a {
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color: #ccc;
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}
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.home-menu li a:hover,
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.home-menu li a:focus {
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animation: menu-hover-anim 0.25s ease-out;
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animation-fill-mode: forwards;
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background: none;
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border: none;
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}
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.link {
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color: #00f;
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text-decoration: none;
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}
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.video {
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text-align: center;
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}
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.video iframe {
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width: 32em;
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height: 18em;
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frameborder: "0";
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}
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/*
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Add transition to containers so they can push in and out.
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*/
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#layout,
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#menu,
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.menu-link {
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-webkit-transition: all 0.2s ease-out;
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-moz-transition: all 0.2s ease-out;
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-ms-transition: all 0.2s ease-out;
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-o-transition: all 0.2s ease-out;
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transition: all 0.2s ease-out;
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}
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/*
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This is the parent `<div>` that contains the menu and the content area.
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*/
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#layout {
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position: relative;
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left: 0;
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padding-left: 0;
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}
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#layout.active #menu {
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left: 150px;
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width: 150px;
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}
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#layout.active .menu-link {
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left: 150px;
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}
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/*
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The content `<div>` is where all your content goes.
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*/
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.content {
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margin: 0 auto;
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padding: 0 2em;
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max-width: 800px;
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margin-bottom: 50px;
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line-height: 1.6em;
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text-align: justify;
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}
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header {
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margin: 0;
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color: #444;
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text-align: center;
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padding: 2.5em 4em 0;
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border-bottom: 1px solid #eee;
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}
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header h1 {
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margin: 0.2em 0;
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font-size: 2.5em;
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font-weight: bold;
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}
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header h2 {
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font-weight: 300;
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color: #888;
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padding: 0;
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margin-top: 0;
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}
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.distinct {
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background-color: #444;
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color: #fff;
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padding: 0.5em 0.5em 0.5em 0.5em;
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}
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2024-04-28 18:19:41 -05:00
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/* @keyframes card-hover-anim { */
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/* to {background-color: #ccc;} */
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/* } */
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/* @keyframes card-text-hover-anim { */
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/* to {color: #222;} */
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/* } */
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.spaced {
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padding: 0.5em 0.5em 0.5em 0.5em;
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margin: 1em 0em 1em 0em;
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}
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svg {
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width: 1em;
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vertical-align: middle;
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}
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.card {
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background-color: #eee;
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text-decoration: none;
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text-align: left;
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}
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.card h1 {
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/* color: #444; */
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}
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.card h2 {
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color: #777;
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}
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.card h3 {
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color: #999;
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}
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/* .card a { */
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/* text-decoration: none; */
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/* display: block; */
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/* } */
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.card:hover {
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animation: card-hover-anim 0.25s ease-out;
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animation-fill-mode: forwards;
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}
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/* .card:hover h3 { */
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/* animation: card-text-hover-anim 0.25s ease-out; */
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/* animation-fill-mode: forwards; */
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/* } */
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.card img {
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vertical-align: bottom;
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float: right;
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padding: 0em 0.1em 0em 0.1em;
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width: 60px;
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}
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.card svg {
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vertical-align: bottom;
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float: right;
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padding: 0em 0.1em 0em 0.1em;
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width: 3em;
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height: auto;
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}
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.content-subhead {
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margin: 50px 0 20px 0;
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font-weight: 300;
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color: #444;
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}
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code {
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font-family: Cascadia;
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}
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.code-block {
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/* background-color: #fdf6e3; */
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background-color: #eee;
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color: #002b36;
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font-family: Cascadia;
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font-size: 0.85em;
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2024-04-28 18:19:41 -05:00
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</style></head><body><div class="pure-g"><div class="pure-u-1-1"><header class="header"><h1> Forte <a href="https://github.com/Xterminate1818/forte" target="_blank"><svg style="padding-bottom: 0.2em;" viewBox="0 0 128 128"><title> View source on GitHub </title><g fill="#181616"><path clip-rule="evenodd" fill-rule="evenodd" d="M64 5.103c-33.347 0-60.388 27.035-60.388 60.388 0 26.682 17.303 49.317 41.297 57.303 3.017.56 4.125-1.31 4.125-2.905 0-1.44-.056-6.197-.082-11.243-16.8 3.653-20.345-7.125-20.345-7.125-2.747-6.98-6.705-8.836-6.705-8.836-5.48-3.748.413-3.67.413-3.67 6.063.425 9.257 6.223 9.257 6.223 5.386 9.23 14.127 6.562 17.573 5.02.542-3.903 2.107-6.568 3.834-8.076-13.413-1.525-27.514-6.704-27.514-29.843 0-6.593 2.36-11.98 6.223-16.21-.628-1.52-2.695-7.662.584-15.98 0 0 5.07-1.623 16.61 6.19C53.7 35 58.867 34.327 64 34.304c5.13.023 10.3.694 15.127 2.033 11.526-7.813 16.59-6.19 16.59-6.19 3.287 8.317 1.22 14.46.593 15.98 3.872 4.23 6.215 9.617 6.215 16.21 0 23.194-14.127 28.3-27.574 29.796 2.167 1.874 4.097 5.55 4.097 11.183 0 8.08-.07 14.583-.07 16.572 0 1.607 1.088 3.49 4.148 2.897 23.98-7.994 41.263-30.622 41.263-57.294C124.388 32.14 97.35 5.104 64 5.104z"></path><path d="M26.484 91.806c-.133.3-.605.39-1.035.185-.44-.196-.685-.605-.543-.906.13-.31.603-.395 1.04-.188.44.197.69.61.537.91zm2.446 2.729c-.287.267-.85.143-1.232-.28-.396-.42-.47-.983-.177-1.254.298-.266.844-.14 1.24.28.394.426.472.984.17 1.255zM31.312 98.012c-.37.258-.976.017-1.35-.52-.37-.538-.37-1.183.01-1.44.373-.258.97-.025 1.35.507.368.545.368 1.19-.01 1.452zm3.261 3.361c-.33.365-1.036.267-1.552-.23-.527-.487-.674-1.18-.343-1.544.336-.366 1.045-.264 1.564.23.527.486.686 1.18.333 1.543zm4.5 1.951c-.147.473-.825.688-1.51.486-.683-.207-1.13-.76-.99-1.238.14-.477.823-.7 1.512-.485.683.206 1.13.756.988 1.237zm4.943.361c.017.498-.563.91-1.28.92-.723.017-1.308-.387-1.315-.877 0-.503.568-.91 1.29-.924.717-.013 1.306.387 1.306.88zm4.598-.782c.086.485-.413.984-1.126 1.117-.7.13-1.35-.172-1.44-.653-.086-.498.422-.997 1.122-1.126.714-.123 1.354.17 1.444.663zm0 0"></path></g></svg></a></h1><h2> Programming Language - Hackathon </h2></header><div class="content"><h2 class="distinct"> Motivation </h2>
|
2024-04-28 17:11:48 -05:00
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In February of 2024, I competed at RowdyHacks during the 9th
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annual Hackathon. This was my second time attending, having
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<a href="/projects/fractal-viewer" class="link">
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placed second the previous year
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</a>.
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My understanding of programming and of Rust had grown significantly over
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that time, and I wanted to one-up myself. I had just finished my Computer
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Organization class, where we learned to program in x86 assembly. The class
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made me realize that the design of an assembly language has a profound
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impact on every higher level language built on-top of it. As a Rust
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programmer who cares a great deal about safety and soundness guarantees, it
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troubles me that I have to compile to an inherently unsafe assembly
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language. I wanted to find out how feasible it would be to write a new
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assembly language designed for easy static analysis and safety guarantees.
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I am very satisfied with the result, which I named Forte.
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<h2 class="distinct"> Specifications </h2><h3> Instructions </h3>
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Forte is an assembly language and bytecode for a hypothetical 128-bit
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processor. It contains 26 instructions, but no directly exposed registers.
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<div class="pure-g"><table class="striped pure-u-1-2"><thead><th> Name </th><th> Mnemonic </th></thead><tbody><tr><td> Push </td><td> push </td></tr><tr><td> Pop </td><td> pop </td></tr><tr><td> Duplicate </td><td> dup </td></tr><tr><td> Add </td><td> add </td></tr><tr><td> Difference </td><td> diff </td></tr><tr><td> Multiply </td><td> mul </td></tr><tr><td> Divide </td><td> div </td></tr><tr><td> Remainder </td><td> rem </td></tr><tr><td> Bitwise And </td><td> and </td></tr><tr><td> Bitwise Or </td><td> or </td></tr><tr><td> Bitwise Xor </td><td> xor </td></tr><tr><td> Shift Right </td><td> shr </td></tr><tr><td> Shift Left </td><td> shl </td></tr></tbody></table><table class="striped pure-u-1-2"><thead><th> Name (cont.) </th><th> Mnemonic (cont.) </th></thead><tbody><tr><td> Branch Equal </td><td> beq </td></tr><tr><td> Branch Unequal </td><td> bne </td></tr><tr><td> Branch Greater </td><td> bgt </td></tr><tr><td> Branch Lesser </td><td> blt </td></tr><tr><td> Function Start </td><td> fun </td></tr><tr><td> Call </td><td> call </td></tr><tr><td> Return </td><td> ret </td></tr><tr><td> Loop </td><td> loop </td></tr><tr><td> Iterate Loop </td><td> iter </td></tr><tr><td> Begin Execution </td><td> exe </td></tr><tr><td> Store </td><td> sto </td></tr><tr><td> Load </td><td> lod </td></tr><tr><td> Stack Length </td><td> len </td></tr></tbody></table></div><h3> The Three Stacks </h3>
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The stack is an essential part of any assembly language, however it is
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often a point of vulnerability. Stack-smashing and stack-overflow
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vulnerabilities can very easily allow attackers to overwright function
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return addresses, and and execute arbitrary code. This is why Forte uses
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three distinct stacks.
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<h3> The Program Stack </h3>
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The program stack, or p-stack for short, contains all of the state for the
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user-space program. When you push or pop a value in Forte, you are
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interacting with the p-stack. What's most interesting about the p-stack is
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what it does not contain: pointers. There is no way to jump to an address
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on the p-stack, as its contents are considered untrusted.
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<h3> The Control Stack </h3>
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In order to call functions, return addresses must be stored somewhere.
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While most assembly languages place these on the stack alongside other
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values, Forte segregates them into a separate control stack (c-stack for
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short.) This is similar to the "shadow stack" option some compilers use,
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except implemented at a hardware level. The only way to interact with the
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c-stack is through call and return instructions.
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<h3> The Function Stack </h3>
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Most assembly languages have a "jump" instruction which moves the program
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counter to an arbitrary point in memory. This is useful but not
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particularly safe. Forte only allows jumping to valid functions. The
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locations of these functions are kept in the function stack (f-stack.)
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Functions are added to the f-stack after they are validated during the
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warmup phase, which I will discuss next.
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<h3> Warmup </h3>
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When a Forte program begins, it does not immediately start executing
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instructions. Instead, it validates the programs correctness and builds
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the f-stack. Every <code>fun</code> (function start) instruction will
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push the address of that instruction to the f-stack. Every instruction that
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interacts with the stack will increment or decrement an internal register
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accordingly. If this value value falls below zero or above the maximum
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stack size, then the program is determined to be unsafe and execution
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is cancelled before it begins. The warmup phase will take O(N) time,
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where N is the number of instructions.
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<h3> Recital </h3>
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After the <code>exe</code> (begin execution) instruction is reached, the
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Recital phase begins. The function pointer returns to the address at the
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top of the f-stack, which was the last defined function. When the program
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counter reaches the <code>exe</code> again, the program has terminated
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successfully. This combination of design decisions means that the program
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counter can never be lower than the first function address, or larger than
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the execution instruction. This makes arbitrary code execution attacks more
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difficult to pull off.
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<h2 class="distinct"> Safety </h2>
|
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Creating a memory safe assembly language presents much different challenges
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from a compiled language like Rust. There are no compile-time checks or
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guarantees, any string of bytes could be interpreted as a "program." The core
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design principle of Forte is to make unsecure programs impossible (or at least
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very difficult) to express, and to make static analysis simple. This is a delicate
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balance to strike - limiting Forte's capabilities necessarily makes it more
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cumbersome and less performant.
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</div></div></div></body></html>
|
