import Data.Ratio

mod2And5 :: Integral a => a -> a
mod2And5 x
    | mod x 2 == 0 = mod2And5 (div x 2)
    | mod x 5 == 0 = mod2And5 (div x 5)
    | otherwise    = x

solve :: (Read a, Show a, Integral a) => a -> a -> a
solve n d
    | mod2And5 d' > 1 = -1
    | otherwise       = read . (: "") . last . reverse . dropWhile (== '0') . reverse . show $ t
    where
        d' = denominator $ n % d
        t  = solve2 n d

solve2 :: Integral a => a -> a -> a
solve2 n d
    | mod n d == 0 = div n d
    | otherwise    = solve2 n' d
    where
        n' = (n - d * (div n d)) * 10

main = do
    n <- readLn
    m <- readLn
    print $ solve n m