import Data.List (sort)

solve :: String -> String
solve s = if x /= 1
            then "Impossible"
            else if (length $ filter (== z) s) > 1
                then "Impossible"
                else y
    where
        x = length y
        y = f $ sort s
        z = head y
f :: String -> String
f [] = []
f (x:y:zs)  | x == y    = f zs
            | otherwise = x : f (y:zs)
main :: IO ()
main = getLine >>= putStrLn . solve