defmodule Main do
  def input, do: IO.read(:line) |> String.trim
  def ii, do: input() |> String.to_integer
  def li, do: input() |> String.split |> Enum.map(&String.to_integer/1)
  def yn(b), do: IO.puts(if b, do: "Yes", else: "No")

  def comma(x) do
    s = Integer.to_string(x) |> String.graphemes
    {a, b} = Enum.split(s, rem(length(s), 3))

    [a] ++ (b |> Enum.chunk_every(3))
    |> Enum.join(",")
    |> String.trim_leading(",")
  end

  import Bitwise

  def main do
    [a, b] = li()

    if band(a, b) == a do
      cnt = bit_count(bxor(a, b))
      div(2 ** cnt, 2)
    else
      0
    end
    |> IO.puts
  end

  def bit_count(0), do: 0
  def bit_count(x) do
    if (x &&& 1) == 1 do
      1 + bit_count(x >>> 1)
    else
      bit_count(x >>> 1)
    end
  end
end