// 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;
    vll f(n + 1);
    f[0] = a;
    f[1] = b;
    for (int i = 2; i < f.size(); i++) {
        f[i] = f[i - 1] ^ f[i - 2];
    }
    cout << f[f.size() - 1] << endl;

    system("pause");
}