text: with r as (
      select hacker_id, name, count(1) challenges_created
      from hackers
      join challenges using (hacker_id)
      group by hacker_id, name
  )
  select *
  from r
  where challenges_created not in 
  ( 
      select challenges_created from r group by challenges_created having count(1) > 1 
      minus
      select max(challenges_created) from r
  )
  order by challenges_created desc, hacker_id;
  
  