> lines' :: String -> [String]
> lines' [] = []
> lines' (x:xs) = if x == '\n' then "" : xss
>                 else (x : head0 xss) : tail0 xss
>    where xss = lines' xs

> head0 [] = []
> head0 (ys:yss) = ys

> tail0 [] = []
> tail0 (ys:yss) = yss

> main = interact (unlines . lines')