import Data.List

main = do
  s <- getLine
  maybe (putStrLn "Impossible") (mapM_ putStrLn) (kokushi s)

kokushi s = case sort (map length (group (sort s))) of
  [1,1,1,1,1,1,1,1,1,1,1,1,1] -> Just $ map return "abcdefghijklm"
  [1,1,1,1,1,1,1,1,1,1,1,2] -> Just $ ["abcdefghijklm" \\ s]
  _ -> Nothing