#include"bits/stdc++.h"
using namespace std;
int main() {
	long int a0, a1, n; cin >> a0 >> a1 >> n;
	if (n % 3 == 0) {
		cout << a0 << endl; return 0;
	}
	else if (n % 3 == 1) {
		cout << a1 << endl; return 0;
	}
	else {
		long int m = a0 ^ a1;
		cout << m << endl;
	}
}