#include<iostream>

using namespace std;

int main() {
  // f_k = f_{k-1} + f_{k-2}
  
  long k1, k2, n;
  cin >> k1 >> k2 >> n;


  if (n%3 == 0) cout << k1 << endl;
  else if (n%3 == 1) cout << k2 << endl;
  else cout << (k1 ^ k2) << endl;
}