#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000

int main(){
	
	long long ans[3];
	cin>>ans[0]>>ans[1];
	ans[2] = ans[0] ^ ans[1];
	
	long long n;
	cin>>n;
	
	cout<<ans[n%3]<<endl;
	
	return 0;
}