using System;

namespace No333
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            string[] data = Console.ReadLine().Split(' ');
            int a = int.Parse(data[0]);
            int b = int.Parse(data[1]);
            int count = 0;

            if (a < b)
                count = b - 2;
            else
                count = 1999999999 - b;

            Console.WriteLine(count);
        }
    }
}