#include<bits/stdc++.h>

using namespace std;
using ll=long long;
#define rep2(i, a, n) for(int i = (a); i < (n); i++)
#define rep(i, n) rep2(i,0,n)

int main(){
  cin.tie(nullptr);ios_base::sync_with_stdio(false);
  ll n,a[3];
  cin>>a[0]>>a[1]>>n;
  a[2]=a[0] xor a[1];
  cout<<a[n%3]<<endl;
}