 Yes, I understand.
( Yes ( , ( I ( understand . ) ) ) )
(ROOT (S (INTJ (UH Yes)) (, ,) (NP (PRP I)) (VP (VBP understand)) (. .)))
I don't understand at all.
( I ( ( ( do n't ) ( understand ( at all ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBP do) (RB n't) (VP (VB understand) (ADVP (IN at) (DT all)))) (. .)))