#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>
//---------------------------
using namespace std;
//---------------------------
#define REP(i,n) for(int i = 0; i < (n); i++)
#define P(x) cout << (x) << "\n"
//---------------------------


int main(){
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);



  long long N;
  long long a,b,c;
  cin >> a >> b >> N;
  long long ans;
  if (N % 3 == 0) {
    ans = a;
  }else if(N % 3 == 1){
    ans = b;
  }else{
  c = b ^ a;
  ans = c;
}
  P(ans);
  return 0;
}