#include <iostream>
using namespace std;

int main()
{
    unsigned long long F0, F1, N;
    cin >> F0 >> F1 >> N;
    if (N % 3 == 0)
    {
        cout << F0 << endl;
    }
    else if (N % 3 == 1)
    {
        cout << F1 << endl;
    }
    else
    {
        unsigned long long ans;
        ans = F0 ^ F1;
        cout << ans << endl;
    }
    return 0;
}