Hello, I’m not sure if this question interests you, but it interests me.

Based on your experience, what are the most toxic communities in the world of competitive programming and the most helpful communities, from when you were a beginner to when you became good at it (CP world) ?

For me the answer is Codeforces as one of the most toxic communities especially for beginners and atcoder and usaco as the most helpful one. (I hope nobody take it personally but that's My opinion).

Hello, I have trying for a while to solve this problem called Xor Sum the problem but i almost got no idea what should i do next after trying for a while i know that a+b=2*(a&b) + u ===> (u=a^b) so v=a+b >= u . But still can't figure what should i do next so i will be glad if you give some kind of hint. thanks in front.