#if !defined(__clang__) && defined(__GNUC__)
#include <bits/stdc++.h>
#else
#include <cstdlib>
#include <climits>
#include <iostream>
#include <cstdint>
#include <vector>
#include <string>
#include <complex>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <utility>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <regex>
#endif //  !defined(__clang__) && defined(__GNUG__)
#if 0
#include <boost/lexical_cast.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/multi_array.hpp>
#include <boost/optional.hpp>
#include <boost/math/common_factor_rt.hpp>
#endif

using namespace std;

int main()
{
    uint64_t F0, F1, N;
    std::cin >> F0 >> F1 >> N;

    uint64_t r = N % 3;
    uint64_t ans;

    if (r == 0) {
        ans = F0;
    }
    else if (r == 2) {
        ans = F0 ^ F1;
    }
    else {
        ans = F1;
    }

    std::cout << ans << std::endl;

    return 0;
}