module Main where

import Data.List (group, sort)

main :: IO ()
main = getLine >>= mapM_ putStrLn . palindromes

palindromes :: String -> [String]
palindromes [] = [""]
palindromes [x] = [[x]]
palindromes xs | head xs == last xs = (++)
                                      <$> ((++)<$> [[head xs]] <*> (palindromes . tail . init) xs)
                                      <*> [[last xs]]
               | otherwise          = candidates $ branches xs
    where
        branches xs = map head . group . sort . concatMap (palindromes . ($xs)) $ [tail, init, tail . init]
        maxlen = maximum . map length
        candidates xs = filter (\x -> length x == maxlen xs) xs