#include<stdio.h>
int main()
{
	long long int a, b;
	scanf("%lld %lld", &a, &b);
	long long int n = 0;
	n = a * n + b;
	if (n == 0)
		printf("1\n");
	else
	{
		n = a * n + b;
		if (n == 0)
			printf("2\n");
		else
			printf("-1\n");
	}
	return 0;
}