main :: IO ()
main = interact $ palDecomp ['a'..'z'] . read

palDecomp :: [Char] -> Int -> String
palDecomp (c:cs) 1 = [c]
palDecomp (c:cs) n
  | even n = [c] ++ palDecomp cs (n-1) ++ [c]
  | otherwise = [c] ++ palDecomp (c:cs) (div (n-1) 2 + 1) ++ [c]