Max players per rank

Well, hello to you, I am at present in search of a plugin which allows to make so that we can define a specific number of people for a rank! I give some explanation.

Imaginon, there exists a Police rank.

People would want to join the rank police via a panel which I have already made and when 3 people will join if one 4 eme tries to join it will tell him(her) this job(business) and at present heights wait that he(it) releases itself. Here we are, I hope that a person will be to find me this, thank you of your understanding!

Sorry for mistakes​