How many athletes from region 151 have won a medal?
athletes refer to person_id; region 151 refers to region_id = 151; won a medal refers to medal_id <> 4;
SELECT COUNT(T3.person_id) FROM competitor_event AS T1 INNER JOIN games_competitor AS T2 ON T1.competitor_id = T2.id INNER JOIN person_region AS T3 ON T2.person_id = T3.person_id WHERE T3.region_id = 151 AND T1.medal_id != 4