select s.hacker_id, h.name from submissions as s 
			inner join Challenges as c on s.challenge_id=c.challenge_id
			inner join Difficulty as d on d.difficulty_level=c.difficulty_level
			inner join Hackers as h on h.hacker_id=s.hacker_id 
where d.score=s.score 
group by s.hacker_id,h.name having count(*)>1 
order by count(*) desc, s.hacker_id;