local a, b = io.read("*n", "*n")
if b < a then a, b = b, a end
local c, d = 0, 0
z = a
while 0 < z do
  c = c + 1
  z = math.floor(z / 2)
end
z = b
while 0 < z do
  d = d + 1
  z = math.floor(z / 2)
end
if c < d then
  print(a)
else
  local mul = 1
  for i = 1, c - 1 do mul = mul * 2 end
  print(mul - 1)
end