Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE services ( service_id number, service_type_code text )
TABLE: CREATE TABLE participants_in_events ( event_id number, participant_id number )
TABLE: CREATE TABLE events ( event_id number, service_id number, event_details text )
TABLE: CREATE TABLE participants ( participant_id number, participant_type_code text, participant_details text )

### Question ###
What are all the distinct participant ids who attended any events?

### Accurate SQL ###

SELECT COUNT(DISTINCT participant_id) FROM participants_in_events