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SELECT h.hacker_id, h.name FROM hackers h, difficulty d, challenges c, submissions s
WHERE h.hacker_id = s.hacker_id AND s.challenge_id = c.challenge_id AND c.difficulty_level = d.difficulty_level AND s.score = d.score
GROUP BY h.hacker_id, h.name
HAVING count(h.hacker_id) > 1
ORDER BY count(h.hacker_id) DESC, h.hacker_id ASC