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.
( I ( ( do not ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP do) (RB not)) (. .)))