module Main where

import qualified Data.ByteString.Char8 as BS
import Data.Char
import Data.String
import Data.List
import Data.Maybe
import Control.Monad

type Width = Int
type Height = Int
type Rectangle = (Width, Height)
type Target = [Int]
type OutputValue = [[BS.ByteString]]
type InitialValue = OutputValue

main :: IO ()
main = do
  [h, w] <- map (fst . fromJust . BS.readInt) . BS.words <$> BS.getLine
  xn <- replicateM h $ map (fst . fromJust . BS.readInt) . BS.words <$> BS.getLine
  flatten <- return . sort $ concat xn
  let r = toOutputValue (w, h) flatten []
  mapM_ (putStrLn . BS.unpack . BS.unwords) r

toOutputValue :: Rectangle -> Target -> InitialValue -> OutputValue
toOutputValue (n, count) ls init
  | count > 0 = toOutputValue (n, count - 1) (drop n ls) (map (BS.pack . show) (take n ls) : init)
  | otherwise = reverse init