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

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