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

int main() {
  int64_t f0, f1, n;
  cin >> f0 >> f1 >> n;
  if (n % 3 == 0) cout << f0 << endl;
  if (n % 3 == 1) cout << f1 << endl;
  if (n % 3 == 2) cout << (f0 ^ f1) << endl;
  return 0;
}