Which service id and type has the least number of participants?
select t3.service_id, t4.service_type_code from participants as t1 join participants_in_events as t2 on t1.participant_id = t2.participant_id join events as t3 on t2.event_id = t3.event_id join services as t4 on t3.service_id = t4.service_id group by t3.service_id order by count(*) asc limit 1