using System;

public class Hello
{
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var ans = getAns(a, b);
        Console.WriteLine(ans);
    }
    static int getAns (int a, int b)
    {
        if (b == 0) return 1;
        if (a == -1) return 2;
        return -1;
    }
}