<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
</head>
<body>
<canvas id="area" style="width:600px;height:300px;">
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</canvas>
<script>
var c = document.getElementById("area");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(70,70,40,0,Math.PI*2,false);
ctx.stroke();
</script>
</body>
</html>