Xor

ll a, b, q;
    cin >> a >> b >> q;
    ll f1 = a, f2 = b;
    ll f=0;
    for (int i = 1; i <= q;i++)
    {
        ll f3 = f2 ^ f1;
        // cout << "f1 :" << f1 << "   "
        //      << "f2 :" << f2 << nl;
        f =f3^f2;
        f1 = f2;
        f2 = f3;
    }
    cout << f;