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

int main(){
  ll F_0,F_1,N;cin>>F_0>>F_1>>N;
  if(N%3==0)cout<<F_0<<endl;
  if(N%3==1)cout<<F_1<<endl;
  if(N%3==2)cout<<(F_0^F_1)<<endl;
}