#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <iterator>
#include <cmath>
#include <iomanip>
using namespace std;

using ull = unsigned long long;
using ll = long long;

int main()
{
    ull f0,f1,n;
    cin >> f0 >> f1 >> n;


    ull f2 = f0 ^ f1;

    ull data[3] = {f0,f1,f2};

    cout << data[n % 3]  << endl;
}