#include <bits/stdc++.h>
#define ll long long
using namespace std;

int main()
{
    ll n;
    vector<ll> f(n+1,0);
    cin >> f[0] >> f[1] >> n;
    for(ll i = 2; i <= n; i++) f[i] = f[i-1] ^ f[i-2];

    cout << f[n] << endl; 


    return 0;
}