select H.hacker_id, name 
from Difficulty D
join Challenges C on D.difficulty_level = C.difficulty_level
join Submissions S on C.challenge_id = S.challenge_id
join Hackers H on H.hacker_id = S.hacker_id
where S.score = D.score
GROUP BY 1, 2
HAVING COUNT(S.challenge_id) > 1
ORDER BY COUNT(S.challenge_id) DESC, 1;