I really don't.
( I ( really ( ( do n't ) . ) ) )
(ROOT (S (NP (PRP I)) (ADVP (RB really)) (VP (VBP do) (RB n't)) (. .)))
I do not want to.
( I ( ( ( do not ) ( want to ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP do) (RB not) (VP (VB want) (PP (TO to)))) (. .)))