import strutils, sequtils, math

let
  ac = readLine(stdin).split.map parseFloat
  (A, C) = (ac[0], ac[1])
  bOdr = max(A.log2, C.log2).int + 1
var
  b = ""

for i in 0 ..< bOdr:
  proc trfm(x: float): int = x.int.toBin(bOdr)[i .. i].parseInt
  b.add (C.trfm - A.trfm).abs

var ans = 0
while b != "":
  if b[0] == '1': ans += 2 ^ (b.len - 1)
  b = b[1 .. ^1]

echo ans