#include<iostream>
#include<climits>
#include<cstdlib>
#include<algorithm>
#include<vector>
#include<map>
using namespace std;
int main(){
    long long int f[2],ans;
    int n;
    cin >> f[0] >> f[1] >> n;
    if(!n)n=3;
    if(n%3!=2)ans = f[n%3];
    else ans = (f[0]^f[1]);
    cout << ans <<endl;
}