function dF(s) {
    var s1 = unescape( s.substr(0, s.length - 1) );
    var t = "";

    for (i = 0; i < s1.length; i++) {
        t += String.fromCharCode(s1.charCodeAt(i) - s.substr(s.length-1,1));
    }
    document.write(unescape(t));
}