How to make dynamic limit in postgres query?

Question

PostgreSQL

Good afternoon,
The following request is not processed:

UPDATE m_hotels set firm_id = 2 where id in (select id from m_hotels order by random() limit (count(m_hotels) / 3 ));

ERROR: aggregate functions are not allowed in LIMIT
LINE 1: ...(select id from m_hotels order by random() limit (count(m_ho...
^
********** Error ***** *****

What could be the reason?

Answer 1

But after all, they directly wrote what the error was:
Aggregate functions cannot be used in LIMIT