#include<iostream>
#include<vector>
#include<bitset>
#include<algorithm>
#include<cmath>
using namespace std;
int main(){ 
    long long a,b,n;
    cin >> a >> b >> n;
    if(n%3==0)  cout << a;
    else if(n%3==1) cout << b;
    else    cout << (a^b);
    return 0;
}