import Data.List (elem)

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

  putStrLn $ if m `mod` 2 /= 0 && m `mod` 5 /= 0
    then "-1"
    else [head $ dropWhile (\c -> c=='0'||c=='.') $ dropExp $ reverse $ show $ fromIntegral n/fromIntegral m]

dropExp :: String -> String
dropExp s
  | 'e' `elem` s = tail $ dropWhile (/='e') s
  | otherwise = s