30 minutes time break after the last appointment

Hello, I have a problem:
I would like to have 30 minutes break after the next started time.
For example:
First appointment: 09:00 - 10:00
Second appointment: 10:30 - 11:30
Third appointment: 12:00 - 13:00 etc..

Can you help me how can I set it?
Thanks your answer!

Imre