module Main where

import Maybe (isJust)

-- all possible moves
moves :: Int-> [Int]
moves x = filter ((<) 0) (map (\n-> x- n) [1,2,3])

-- wins x returns Just n if we can win by taking n
wins :: Int-> Maybe Int
wins x = case filter mustlose (moves x) of 
             m:_ -> Just (x-m)
             [] -> Nothing

-- as was
mustlose :: Int-> Bool 
mustlose x = x==1 || all (isJust.wins) (moves x)

-- only testing
main = mapM_ (\n-> putStrLn (show n ++ 
                             case wins n of 
			       Just m -> " wins with "++ show m
                               Nothing -> " loses")) [1..]