I don't know.
( I ( ( ( do n't ) know ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP do) (RB n't) (VP (VB know))) (. .)))
I have not the first clue.
( I ( ( have ( not ( the ( first clue ) ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP have) (NP (RB not) (DT the) (JJ first) (NN clue))) (. .)))