#include <bits/stdc++.h>

inline long nextInt(void) {
  long temp;
  std::cin >> temp;
  return temp;
}

int main() {

  long F[3];
  long N;

  F[0] = nextInt();
  F[1] = nextInt();
  N    = nextInt();

  F[2] = F[0] ^ F[1];

  std::cout << F[N%3] << std::endl;
  
  return 0;
}