#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <stack>
#include <algorithm>
#include <string>
#include <map>
#include <iterator>
#include <set>
#include <queue>
#include <bitset>
#include <cassert>

using namespace std;

int main() {

    unsigned long long F0, F1, N;
    cin >> F0 >> F1 >> N;
    unsigned long long F2 = F0 ^F1;
    switch (N % 3) {
        case 0:
            cout << F0 << endl;
            break;
        case 1:
            cout << F1 << endl;
            break;
        case 2:
            cout << F2 << endl;
            break;
    }


}