We've got to think.
( We ( ( 've ( got ( to think ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP 've) (VP (VBN got) (S (VP (TO to) (VP (VB think)))))) (. .)))
We need to think.
( We ( ( need ( to think ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP need) (S (VP (TO to) (VP (VB think))))) (. .)))