Hello codeforces!
This round was very cool, I won't deny that. But, many people "precomputed" answers for E. How is it possible? Let me introduce you to OEIS. This is an online encylopedia of series and sequences, and it's very well-known. Consider the output of sample 4 (12164510040883200). It's a pretty random number, right?
No. Let's see what happens. Paste this URL: https://oeis.org/search?q=12164510040883200&language=english&go=Search We can see that the result is a sequence of integers 1, 3, 40, 1260, 72576, 6652800, 889574400, 163459296000, 39520825344000, 12164510040883200, 4644631106519040000, 2154334728240414720000, 1193170003333152768000000, 777776389315596582912000000 which turn out to be the solutions for problem E.
Problem E was solved by many in a similar fashion, and it's extremely unfair to the others if people who cheated get away with it. I request you to scrap problem E, or make the round unrated.
Thank you!
vovuh, MikeMirzayanov Can you please explain?
I didn't pre computed but let me tell you ,its allowed to use OEIS in CP.
Using OEIS is not against the rules, and I'm fine with people who used it to solve E, even when I solved it using DP.
it's not a good reason to make a round unrated, in about 30% of cf contest(div2 and div3), there is a problem witch its solution can be found out hardly on internet, and it's not a good idea to make 30% of contests unrated because of that :)