import Text.Parsers.Frisby



additive :: forall s . PM s (P s Integer)
additive = mdo
    additive <- newRule $ multitive <> char '+' ->> additive ## uncurry (+) // multitive
    multitive <- newRule $ primary <> char '*' ->> multitive ## uncurry (*) // primary
    primary <- newRule $ char '(' ->> additive <<- char ')' // decimal
    decimal <- newRule $ many1 (oneOf ['0' .. '9']) ## read
    return additive


main = do
    c <- getContents
    print (runPeg additive c)