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

int main(){
    ll A, B, N;
    cin >> A >> B >> N;

    ll M[4][3] = {
        {0, 0, 0},
        {0, 1, 1},
        {1, 0, 1},
        {1, 1, 0}
    };

    ll ans = 0;
    for (int k = 0; k < 62; k++){
        int s = ((A>>k&1ll)<<1)+(B>>k&1ll);
        ans |= M[s][N%3]<<k;
    }

    cout << ans << endl;
}