Count only distinct observation based in ID - data in long format

I have a dataset of a company events. An event can have many participants, that is why my data is a long format. There can be many rows for a single event. I just would like to create a frequency table of event types (outdoors vs indoor). I create a pivot table but since my data in a long format it is over-counting the event types. Please see the attach excel spreadsheet for more information.

Thank you very much in advance!
Marvin