How to set the same answer can only be edited by one person at the same time

Content

Hi, Everyone

When I edited the content of the answer, I found that the same answer could be edited by more than one person at the same time, but the saved content was modified by the last person. This kind of operation is unreasonable. I want to amend this rule to be changed like this: the same answer can only be modified by one person at the same time. When other people open, the system will prompt this article to be edited by ***. Please contact the corresponding Personnel handling.

Please tell me what to do. 

Thanks

Aaron