I think we can go further from 47 but I don't know till when it will get better

same idea used but with little extra help 184968390 ,184969180 and 184969946 as you can see the more primes I checked separately the better the time gets

person who actually wrote this blog

As a tester I think there should be a section to ask for contribution.

Once upon a time cf contests were good filled with beautiful tasks and nice ideas. And among all of them Persian contests were filled with nice graph dp problems as once Clix said. But now I see these contests filled with adhoc tasks and not quite programming for example this contest could be a perfect atcoder contest but in cf I expect seeing cf-like contests as I once did. I know people have different tastes of problems but in my opinion there are many nice sites for solving adhoc problem so let cf be for non-adhoc ones.

As far as I check all the problems either in div1/div2 had some people FSTed so I think that's the reason.