#include<iostream>
#include<stdio.h>
using namespace std;
int main(void)
{
	long long f0, f1, n;

	cin >> f0 >> f1 >> n;

	if (n % 3 == 0)
		cout << f0 << endl;
	else if (n % 3 == 1)
		cout << f1 << endl;
	else  printf("%lld\n", f0^f1);
	return 0;
}