import Data.List

groupInto n [] = []
groupInto n l  = take n l : groupInto n (drop n l)

doEveryOther fn (x:[])  = [x]
doEveryOther fn []     = []
doEveryOther fn (x:xs:xss) = x : fn xs : (doEveryOther fn xss)

decrypt list n = concat . transpose . doEveryOther reverse $ groupInto n list

main = do getContents >>= mapM putStrLn . map (\(x:xs) -> decrypt (head xs) (read x)) . groupInto 2 . takeWhile (/= "0") . lines