data Color = R | B deriving Show
data Tree elt = E | T Color (Tree elt) elt (Tree elt) deriving Show

empty :: Tree elt
empty = E

member :: Ord elt => elt -> Tree elt -> Bool
member x E = False
member x (T _ a y b) 	| x < y 	= member x a
			| x==y		= True
			| x > y		= member x b

insert :: Ord elt => elt -> Tree elt -> Tree elt
insert x s	= makeBlack (ins s)
	where 	ins E = T R E x E
		ins (T color a y b) 	| x < y 	= balance color (ins a) y b
					| x == y 	= T color a y b
					| x > y		= balance color a y (ins b)
		makeBlack (T _ a y b)	= T B a y b
	
		balance B (T R (T R a x b) y c) z d	= T R (T B a x b) y (T B c z d)
		balance B (T R a x (T R b y c)) z d 	= T R (T B a x b) y (T B c z d)
		balance B a x (T R (T R b y c) z d)	= T R (T B a x b) y (T B c z d)
		balance B a x (T R b y (T R c z d))	= T R (T B a x b) y (T B c z d)
		balance color a x b 	 		= T color a x b