#include "bits/stdc++.h"
using namespace std;

#define REP(i, n) for(int i=0; i<(n); i++)
#define int long long

int N;
signed main()
{
    int F[3];
    cin >> F[0] >> F[1] >> N;
    F[2] = F[1] ^ F[0];
    cout << F[N%3] << endl;
    return 0;
}