#include <iostream>
using namespace std;
typedef long long LL;
int main(int argc, char* argv[])
{
	LL F[2];
	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;
	}

	for (LL i=2;i<=N;i++){
		F[0]=F[0]^F[1];
		swap(F[0],F[1]);
	}
	cout<<F[1]<<endl;
	return 0;
}