#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
using namespace std;
typedef long long ll;
const int mod=1e9+7;
int main(){
	ll f0,f1,n;
	cin>>f0>>f1>>n;
	n%=3;
	cout<<(n==0?f0:n==1?f1:f0^f1)<<endl;
}