#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef pair<int,int> P;
 
const int INF = 1e9;
const int mod = 1e9+7;
const double EPS = 1e-10;
const double PI = acos(-1.0);

int main()
{
    ll f[3],n;
    cin >> f[0] >> f[1] >> n;
    f[2] = f[1]^f[0];
    cout << f[n%3] << endl;

    return 0;
}