function rot13(input) {
  var output = "";
  for (var i = 0; i < input.length; i++ ) {
    // Letters A-Z (code 65-90):
    if (input.charCodeAt(i) >= 65 && input.charCodeAt(i) <= 90) {
      output = output + String.fromCharCode(65 + (((input.charCodeAt(i) - 65) + 13) % 26));
    } else {
      // Letters a-z (code 97-122):
      if (input.charCodeAt(i) >= 97 && input.charCodeAt(i) <= 122) {
  output = output + String.fromCharCode(97 + (((input.charCodeAt(i) - 97) + 13) % 26));
      } else {
  output = output + input.charAt(i);
      }
    }
  }
  output = "<a href=\"mailto:" + output + "\">" + output + "</a>";
  return output;
}