using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Yuki
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] s = Console.ReadLine().Split(); ;
            int a = int.Parse(s[0]);
            int b = int.Parse(s[1]);
            int ans;

            if (a > b)
            {
                ans = 2000000000 - b - 1;
            }
            else
            {
                ans = b - 2;
                if (b == 0)
                {
                    ans = 0;
                }
            }
            Console.WriteLine(ans);
        }
    }
}