function rot13(str) {
	var arr = [];
	var newStr = "";
		str = str.replace(/[^a-zA-Z0-9 !?.]+/g, "").toUpperCase();
		alert(str);
		for (var i = 0; i < str.length; i++) {
			if (str[i] >="A" && str[i] <="M" ) {
  				arr.push(str.charCodeAt(i) + 13);
  			}
  			else if (str[i] >="N" && str[i] <="Z") {
			arr.push(str.charCodeAt(i) - 13);
		} else {
			arr.push(str.charCodeAt(i));
		}
	}


		for (var j = 0; j < arr.length; j++) {
	  		newStr += String.fromCharCode(arr[j]);
	  	}
	  return newStr;

}


// Change the inputs below to test
rot13("SERR PBQR PNZC");