#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;

int main()
{
    long long int x, y, n, ans;

    cin >> x >> y >> n;
    for(long long int i=0; ans = x, i<n; i++){
        x ^= y;
        swap(x, y);
    }
    cout << x << endl;

    return 0;
}