function heidiDecode(hex) {
    var str = '';
    var shift = parseInt(hex.substr(-1));
    hex = hex.substr(0, hex.length - 1);
    for (var i = 0; i < hex.length; i += 2)
      str += String.fromCharCode(parseInt(hex.substr(i, 2), 16) - shift);
    return str;
}

console.log(heidiDecode('71786675786E782D484075393'));

var isBrowser=new Function("try {return this===window;}catch(e){ return false;}");

if (isBrowser()) {
    document.write(heidiDecode('71786675786E782D484075393'));
}