need n't waste their time on it 
(ROOT (S (VP (VB need) (RB n't) (VP (VB waste) (NP (PRP$ their) (NN time)) (PP (IN on) (NP (PRP it)))))))
(ROOT (S (VP (VB ) (RB ) (VP (VB ) (NP (PRP$ ) (NN )) (PP (IN ) (NP (PRP )))))))