#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int a,b,n;
  cin>>a>>b>>n;
  n%=3;
  if(n==0) cout<<a<<endl;
  if(n==1) cout<<b<<endl;
  if(n==2) cout<<(a^b)<<endl;
  return 0;
}