import std.stdio, std.conv, std.math, std.string, std.range, std.array,
       std.algorithm;

void main(){
  auto buf = readln().strip().split().map!(to!long)();
  long a = buf[0], b = buf[1];

  long t = buf[2] % 3;

  switch(t) {
    case 0:
      writeln(buf[0]);
      break;
    case 1:
      writeln(buf[1]);
      break;
    case 2:
      writeln(buf[0] ^ buf[1]);
      break;
    default:
      assert(false);
  }

}