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<html lang="es">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
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<body>
<canvas width="600" height="400"></canvas>
<script>
var pantalla = document.querySelector("canvas");
var pincel = pantalla.getContext("2d");
pincel.fillStyle = "black";
pincel.beginPath();
pincel.moveTo(45, 45);
pincel.lineTo(45, 400);
pincel.lineTo(550, 400), pincel.fill();
pincel.fillStyle = "white";
pincel.beginPath();
pincel.moveTo(67, 90);
pincel.lineTo(67, 375);
pincel.lineTo(475, 375), pincel.fill();
</script>
</body>
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