#include<iostream>
#include<string>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<map>
#include<vector>
#include<queue>
#include<utility>
using namespace std;
typedef long long int ll;

int main(){

  ll f[3], n;
  cin >> f[0] >> f[1] >> n;
  f[2]=f[0]^f[1];
  cout << f[n%3] << endl;


  return 0;
}