mysql - SQL COUNT on GROUP BY -


this code got far 

select users_id,problem_id  'submission' status = "ac"  group users_id,problem_id

i getting these results

+----------+------------+ | users_id | problem_id | +----------+------------+ |        1 |          1 | |        1 |          2 | |        1 |          3 | |        2 |          1 | |        2 |          3 | +----------+------------+

i want get

+----------+------------+ | users_id | problem_id | +----------+------------+ |        1 |          3 | --  because there 3 results user_id 1 |        2 |          2 | -- , there 2 results user_id 2 +----------+------------+

so problem_id how many rows getting query each user.
how accomplish this?

edit:

i forgot mention table contains duplicates of same problem example.
got problem id of 1 , in database there 2 rows same user , status "ac" want 1 of them.

this should work:

select users_id, count(distinct problem_id) `submission` status = 'ac'  group users_id

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