-- Try yukicoder
-- author: Leonardone @ NEETSDKASU

import Data.Bits

main = interact $ show . solve . map read . words

solve :: [Integer] -> Integer
solve [a, b] = ans
    where
        c = xor a b
        e = a .&. c
        p = popCount c
        ans = if e /= 0 then 0 else
            max 1 $ div (2 ^ p) 2