#include<bits/stdc++.h>

using namespace std;
using ll = 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 ^ b) << endl;
    return 0;
}