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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
//计算n的阶乘n可输入
<script type = "text/javascript">
var n = parseInt(window.prompt('input'));
var mul = 1;
for(var i = 1;i<=n;i++){
mul *= i;
}
document.write(mul);
</script>
</body>
</html>