negation - How to agree with a negative statement: with "yes" or with "no"?

This question here asks about answering negative questions:

I have a completely different question. I want to know:

• how do we agree or disagree with negative statements in English.

Example:

––This is not a duplicate question.

––Yes, it is a new one.

or

––This is not a duplicate question.

––No, it is a new one.