using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = int.Parse(line[0]);
        var b = int.Parse(line[1]);
        var kmax = 2000000000;
        int ans;
        if (a < b) ans = b - 2;
        else ans = kmax - b - 1;
        Console.WriteLine(ans);
    }
}