main :: IO ()
main = do
  n <- readLn :: IO Integer
  m <- readLn :: IO Integer

  print $ if m `mod` 2 /= 0 && m `mod` 5 /= 0
    then -1
    else last $ n`divL`m

divL :: Integer -> Integer -> [Integer]
divL n m
  | n == 0 = []
  | otherwise = n`div`m:divL (n`mod`m*10) m