Why i am unable to submit a solution of past contest (LOCKDOWN TEST 4.0)

as i don’t know in which section(easy,medium,hard(no-way)) this problem is placed so i always go to contest link instead of going into the practice section and search for it.
i badly want to submit this parenthesis ques in lockdown
so any help would be :wink:

Contest Link --> https://www.codechef.com/LDT42020?order=desc&sortBy=successful_submissions