import Data.List as L

main = do
    s <- getLine
    putStr $ showResult $ solve s

solve :: String -> [Char]
solve s = filter success ['a'..'z']
    where success c = (length $ filter (\x -> length x == 2) s') == 7
              where s' = L.group $ sort (c:s)

showResult :: [Char] -> String
showResult [] = "Impossible"
showResult cs = unlines $ map (\x -> [x]) cs