// コピーして使う！
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<long long>;

int main() {
    ll a, b, n;
    cin>>a>>b>>n;
    if (n % 3 == 0) {
        cout << a << endl;
    } else if (n % 3 == 1) {
        cout << b << endl;
    } else {
        cout << (a xor b) << endl;
    }

    system("pause");
}