#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvll;
const ll inf = 1e16;
const ll md = 1000000007;

int main() {
  ll f0,f1,n;
  cin>>f0>>f1>>n;
  ll ans;
  if(n%3==0) ans=f0;
  if(n%3==1) ans=f1;
  if(n%3==2) ans=f0^f1;
  cout<<ans<<endl;
  return 0;
}