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

int main(){
	long long a,b,n;
	cin >> a >> b >> n;
	if(n % 3 == 0){
		cout << a << endl;
	}
	if(n % 3 == 1){
		cout << b << endl;
	}
	if(n % 3 == 2){
		cout << (a ^ b) << endl;
	}
}