批量移动主题时出现“标题已被使用”。如何知道是哪个主题?

Hi.
I’m trying to bulk move a lot of topics from a category to another one, after a phpbb3 import.
However, I have this error. how do I identify the topic that causes this error?

Don’t waste your time, temporarily enable the site setting allow duplicate topic titles to move the topics.

You’re totally right, I didn’t know this setting.