using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static void Main()
    {
        var c = NList;
        var (a, b) = (c[0], c[1]);
        WriteLine(XorMin(a, b));
    }
    static int XorMin(int a, int b)
    {
        var large = Math.Max(a, b);
        var mul = 1;
        while (mul * 2 <= large) mul *= 2;
        return Math.Min(mul - 1, Math.Min(a, b));
    }
}