#include <bits/stdc++.h>

using namespace std;

int main() {
    long long f0, f1, n;
    
    cin >> f0 >> f1 >> n;
    
    if (n % 3 == 0) {
        cout << setprecision(20) << f0 << endl;
    } else if (n % 3 == 1) {
        cout << setprecision(20) << f1 << endl;
    } else {
        cout << setprecision(20) << static_cast<long long>(f1 ^ f0) << endl;
    }
    
    return 0;
}