#include <stdio.h>

int main() {
	long long int f0, f1, n, f;

	scanf("%lld %lld %lld", &f0, &f1, &n);

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