<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>JavaScript Example</title>
</head>
<body>

  <script>
    var a = 10;
    var b = 20;
    var c = a + b; // It adds values of the a and b variables
    document.write(c); // Prints the sum of 10 and 20
  </script>

</body>
</html>
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