I've got this message in the morning this day :

Attention!

Your solution 274855834 for the problem 1999F significantly coincides with solutions Kareem_Elgoker/274855834, Eyad_Abd_El-Mohsen/274908131. Such a coincidence is a clear rules violation. Note that unintentional leakage is also a violation. For example, do not use ideone.com with the default settings (public access to your code). If you have conclusive evidence that a coincidence has occurred due to the use of a common source published before the competition, write a comment to post about the round with all the details. More information can be found at http://mirror.codeforces.com/blog/entry/8790. Such violation of the rules may be the reason for blocking your account or other penalties. In case of repeated violations, your account may be blocked.

My code : 274855834 His code : 274908131

We have used a pre-published combinatorics template from Usaco : the link for the template, you can find the template code after -> Method 2: Factorial Definition (Modular Inverses) — $$$\mathcal{O}(n + \log MOD)$$$

Also there is a proof that I don't cheat in this problem

I made a screencast for this contest and had uploaded it on youtube : https://youtu.be/whG44e-HVuc?si=e0kzzTJ_AvgphR10

SlavicG, flamestorm, mesanu, MikeMirzayanov