#include <bits/stdc++.h>
using namespace std;

void solve() {
  unsigned long long N;
  vector<unsigned long long> v(3);
  cin >> v[0] >> v[1];
  v[2] = v[0] ^ v[1];
  cin >> N;
  cout << v[(N % 3)] << endl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
  getchar();
}