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

int main(){
    ll f0, f1, n;
    cin >> f0 >> f1 >> n;
    ll f2 = f0 ^ f1;
    if(n%3 == 0) cout << f0 << endl;
    else if(n%3 == 1) cout << f1 << endl;
    else if(n%3 == 2) cout << f2 << endl;
    return 0;
}