#include<iostream>
using namespace std;

typedef long long  ll;
int main()
{
    ll F[3],N;
    cin >> F[0] >> F[1] >> N;
    F[2] = F[1]^F[0];
    //cout << F[2] << endl;
    
    F[0] = F[2]^F[1];
    //cout << F[0] << endl;
    
    F[1] = F[0]^F[2];
    //cout << F[1] << endl;

    cout << F[N%3] << endl;
    return 0;
}