#include <iostream>
//using namespace std;
typedef unsigned long long ul;
typedef signed long long ll;

int main(void)
{
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);
  std::cout << std::fixed;
  ul x, y, n;
  std::cin >> x >> y >> n;
  if (n%3==0) std::cout << x << std::endl;
  else if (n%3==1) std::cout << y << std::endl;
  else std::cout << (x^y) << std::endl;
  return 0;
}