import Random
import System.Directory
import System.Environment
import System.Exit
import Monad

swap l a b
	| b > a =  map (swap' b a l) $ zip l [0..]
	| a == b = l
	| a > b = map (swap' a b l) $ zip l [0..]
	where
	swap' a b l (v,k)
		| k == a = l !! b
		| k == b = l !! a
		| otherwise = v

shuffle l = foldM shuffle' l $ reverse $ [1..length l - 1]
	where
	shuffle' l n = randomRIO(0, n-1) >>= return . swap l n

main = do
	a <- getArgs
	main' a
	where
	main' a
		| length a /= 2 = getProgName >>= \x -> putStrLn ("Usage: " ++
		    x ++ " <dir> <num>") >> exitWith (ExitFailure 1)
		| otherwise = do
			d <- getDirectoryContents dir
			l <- filterM (doesFileExist . (++) (dir ++ "/")) d >>=
			    shuffle
			mapM putStrLn $ take num l
		where
		dir = a !! 0
		num = read $ a !! 1