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

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var va = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var nn = va[0] < va[1] ? va[1] - 2 : 2000000000 - va[1] - 1;
            Console.WriteLine(nn);
            Console.ReadLine();
        }
    }
}