#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> pii;
typedef long long int ll;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    ll a, b, c, n;
    cin >> a >> b >> n;
    if (n % 3 == 0)
        cout << a << endl;
    else if (n % 3 == 1)
        cout << b << endl;
    else if (n %3 == 2)
        cout << (a^b) << endl;

}