function mirror(s) {
return s.replace(/([LRFBUD])([2']?)/g, function(m, s, a){
return ((s=='L')?'R':(s=='R')?'L':s) + ((a=='')?"'":(a=='2')?a:'');
});
}
print(mirror("L R' F2 B U2 D'"));
ZnVuY3Rpb24gbWlycm9yKHMpIHsKICByZXR1cm4gcy5yZXBsYWNlKC8oW0xSRkJVRF0pKFsyJ10/KS9nLCBmdW5jdGlvbihtLCBzLCBhKXsKICAgIHJldHVybiAoKHM9PSdMJyk/J1InOihzPT0nUicpPydMJzpzKSArICgoYT09JycpPyInIjooYT09JzInKT9hOicnKTsKICB9KTsKfQpwcmludChtaXJyb3IoIkwgUicgRjIgQiBVMiBEJyIpKTsK