#include<iostream>
using namespace std;
using ll = long long;

int main() {
	ll f0, f1, n;
	cin >> f0 >> f1 >> n;
	n %= 3;
	if (n == 0)cout << f0 << endl;
	else if (n == 1)cout << f1 << endl;
	else cout << (f0^f1) << endl;
}