// yuki 1047 Zero (Novice)
// 2021.8.12

#include <stdio.h>

int main()
{
	int A, B;
	int ans = -1;

	scanf("%d%d", &A, &B);
	if (B == 0) ans = 1;
	else if (A == -1) ans = 2;
	printf("%d\n", ans);
	return 0;
}