#include<iostream>
#include<stdio.h>

using namespace std;

int main(){

    long long int f0, f1, n;
    cin>> f0>> f1>> n;

    long long int ans = f0 ^ f1;
    switch(n%3){
        case 0: cout<< f0<< endl;
                 break;
        case 1: cout<< f1<< endl;
                 break;
        case 2: cout<< ans<< endl;
                 break;
    }

    return 0;
}