using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text;
//using static CompLib.CompLib;
//using DataStructure;

namespace atcoder
{

    class Program
    {
        const int intMax = 1000000000;
        const long longMax = 2000000000000000000;
        static void Main(string[] args)
        {
            var AB = Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
            int A = AB[0];
            int B = AB[1];
            if (A > B)
            {
                int temp = A;
                A = B;
                B = temp;
            }
            var binA = Convert.ToString(A, 2);
            var binB = Convert.ToString(B, 2);
            if (binA.Length < binB.Length)
            {
                Console.WriteLine(A);
            }
            else
            {
                Console.WriteLine(Math.Pow(2, binA.Length - 1) - 1);
            }

        }
    }
}