#include <algorithm>
#include <array>
#include <cstdio>
#include <iostream>
#include <numeric>
#include <optional>
#include <vector>

using namespace std;

int main() {
    int64_t f0, f1, n;
    cin >> f0 >> f1 >> n;
    int64_t ans;
    if (n % 3 == 0)
        ans = f0;
    else if (n % 3 == 1)
        ans = f1;
    else
        ans = f0 ^ f1;
    cout << ans << endl;
    return 0;
}