A, B = map(int, input().split())

ans = 1
for i in range(31):
  if (A >> i & 1) == 1 and (B >> i & 1) == 0:
    ans = 0
  elif (A >> i & 1) == 0 and (B >> i & 1) == 1:
    ans *= 2

if ans == 1:
  print(ans)
else:
  print(ans // 2)