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

using ll = long long;

int main(void) {
	ll F1, F2, K;
	cin >> F1 >> F2 >> K;
	
	if(K % 3 == 0) cout << F1 << "\n";
	if(K % 3 == 1) cout << F2 << "\n";
	if(K % 3 == 2) cout << (F1 ^ F2) << "\n";
	
	return 0;
}