import System.IO



asc r@('\n':_) (x:xs) = asc (x:r) xs
asc r [] = drop 1 $ reverse r
asc r@(s:sx) i@(x:xs)
    | x == ' ' = asc r xs
    | x == '\n' = asc ('\n':r) xs
    | s < x = asc (x:r) xs
    | otherwise = asc r xs

main = interact (asc "\n")