#include <iostream>
#include <cstdint>

using namespace std;

int main() {
    int64_t a, b, c, n;
    cin >> a >> b >> n;
    c = (a ^ b);
    if ((n % 3) == 0) {
        cout << a <<endl;
    } else if ((n % 3) == 1) {
        cout << b <<endl;
    } else {
        cout << c <<endl;
    }

    return 0;
}