I'm really sorry, but I prefer not to explain my reasons, so please don't ask me why I'm doing this, it was hard enough for me to make this decision, and also please don't try to convince me to change my mind.
I'd like to say thank you to everyone who used it, and please accept my sincere apologies for shutting it down.
If you have something good to say about A2OJ (how you used it or how it helped you in any way), I'd love to read that, please send it to the following email (or in a comment here): firstname.lastname@example.org
Also please feel free to take a copy of any data you can access, and if you need some data in a specific format, please send your request to the following email: email@example.com (if the data isn't public, make sure to send from your registered and verified email which can access this data). I'll do my best to fulfill all requests.
Please only use the above email, because soon I'll be deactivating my personal Facebook account again, I'll also deactivate A2 Online Judge.
Edit 1: I'll keep a static version of all Ladders & Categories.
Edit 2: Here's how I generated the ladders, in case if anyone wants to implement it: https://codeforces.com/blog/entry/47442