import "Prelude"

data Exp = Exp String

expToString :: Exp -> String
expToString (Exp s) = s

instance Additive Exp where
    zero = Exp "0"
    Exp a + Exp b = Exp ("(" + a + " + " + b + ")")

instance Ring Exp where
    one = Exp "1"
    neg (Exp a) = Exp ("(-" + a + ")")
    Exp a * Exp b = Exp ("(" + a + " * " + b + ")")
    Exp a - Exp b = Exp ("(" + a + " - " + b + ")")
    fromInteger x = Exp (show x)
    
a = Exp "a"
b = Exp "b"
c = Exp "c"
d = Exp "d"
e = Exp "e"

main = expToString (a + b*c + d*e)
--
((a + (b * c)) + (d * e))