how does problem rating system works I dont think C would be 800 atleast 900, I guess since a lot of people have solved it , it is given 800.

in question B can't we do ans = (1+d)*(1+2*d)

I love these types of questions , hope codeforces will make some rated ones for these..

Thanks a lot

where are these things in C question solution "fflush(stdout) or cout.flush() in C++;". please include these and if not then why it is not needed