#include <iostream>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	LL F[3];
	LL N;
	cin>>F[0]>>F[1]>>N;
	if (N==0){
		cout<<F[0]<<endl;
		return 0;
	}else if (N==1){
		cout<<F[1]<<endl;
		return 0;
	}

	F[2]=F[0]^F[1];
	cout<<F[N%3]<<endl;
	return 0;
}