#include<stdio.h>
int main()
{
	int x, y;
	scanf("%d %d", &x, &y);
	if (x == y)
		printf("0\n");
	else if (y == 0)
		printf("1\n");
	else if (x == 0)
		printf("2\n");
	else
		printf("-1\n");
	return 0;
}