#include <bits/stdc++.h>
#define rep(i, ss, ee) for (int i = ss; i < ee; ++i)
using namespace std;

void solve() {
  int N;
  vector<int> v(3);
  rep(i, 0, 2) { cin >> v[i]; };
  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();
}