module Main ( main ) where

import Control.Monad ( mapM_ )
import System.Environment ( getArgs )

fact :: Integer -> Maybe Integer
fact n = if n < 0 then Nothing else Just (product [1..n])

main :: IO ()
main = do
	argv <- getArgs
        let nums = map (read::String -> Integer) argv ;
	    factNums = map fact nums ;
            resultSet = zip nums factNums in
                mapM_ (putStrLn . formatResult) resultSet
                    where formatResult (a, Nothing) =
                             (show a) ++ "! = undefined"
		          formatResult (a, Just b) =
			     (show a) ++ "! = " ++ (show b)