#include <bits/stdc++.h>

using namespace std;

#define ll long long

int main() {
    ll f0, f1, n;
    cin >> f0 >> f1 >> n;
    
    switch (n % 3) {
        case 0:
            cout << f0 << endl;
            break;
        case 1:
            cout << f1 << endl;
            break;
        case 2:
            cout << (f0 ^ f1) << endl;
            break;
    }
    return 0;
}