#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, e) for (int i = (int)s; i < (int)e; i++)

int main() {
    cin.tie(nullptr);
    
    ll F0, F1, N;
    cin >> F0 >> F1 >> N;
    
    if (N % 3 == 0) cout << F0 << '\n';
    else if (N % 3 == 1) cout << F1 << '\n';
    else cout << (F0 ^ F1) << '\n';
}