#include"bits/stdc++.h"
using namespace std;
int main() {
	long int a0, a1, n; cin >> a0 >> a1 >> n;
	long int m;
	for (int i = 2; i <= n; i++) {
		m = a1 ^ a0;
		a0 = a1; a1 = m;
	}
	cout << m << endl;
}