/*
Enter your query here.
Please append a semicolon ";" at the end of the query and enter your query in a single line to avoid error.
*/
with ranking as
(
select 
  h.hacker_id,
  h.name,
  count(c.challenge_id) counter
from
  hackers h
  join challenges c on h.hacker_id = c.hacker_id
group by 
  h.hacker_id,
  h.name
)
, maximum as
(
select 
  max(counter) max_counter
from ranking
)
, quantity as
(
select 
  counter,
  count(counter) count_counter
from ranking
group by counter
)

select 
  r.* 
from
  ranking r
  join maximum m on r.counter <= m.max_counter
  join quantity q on r.counter = q.counter
where
  q.count_counter = 1 or r.counter = m.max_counter
order by
  r.counter desc,
  r.hacker_id asc