#include <bits/stdc++.h>

int main() {
    unsigned long f0, f1, n;
    std::cin >> f0 >> f1 >> n;

    int f2 = f0 ^ f1;

    if (n % 3 == 0) {
        std::cout << f0 << std::endl;
    } else if (n % 3 == 1) {
        std::cout << f1 << std::endl;
    } else {
        std::cout << f2 << std::endl;
    }

    return 0;
}