import sys
input = lambda: sys.stdin.readline().rstrip()

def get_max_beki(x) -> int:
  "Return max(k which 2**k <= x)."
  # assert x >= 0
  ret = 0
  while 2**(ret+1) <= x:
    ret += 1
  return ret

##################

a, b = map(int, input().split())
if a > b:
  a, b = b, a

aa = get_max_beki(a)
bb = get_max_beki(b)
if aa < bb:
  print(a)
else:
  print(2**aa - 1)