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var pantalla = document.querySelector("canvas");
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pincel.beginPath()
pincel.moveTo(50,50)
pincel.lineTo(50,400)
pincel.lineTo(400,400)
pincel.fill()
pincel.fillStyle="white"
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pincel.moveTo(90,150)
pincel.lineTo(90,360)
pincel.lineTo(310,360)
pincel.fill()
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