#include <bitset>
#include <iostream>
#include <vector>
using namespace std;

int main() {
  long long F0, F1, N;
  cin >> F0 >> F1 >> N;
  vector<long long> F(3);
  F[0] = F0, F[1] = F1, F[2] = F0 ^ F1;
  cout << F[N % 3] << endl;
}