Good morning everyone,
I found out that codeforcs has a new feture that you can star mesanges you sent or someone sent (like when you make someone a friend you click a star).
Look here:
You can easily find any meesange you want fast i think in O(log n) where n is the meesanges you have sent. I think its new and thank you codeforces that you still make awwesome things (although you are being late iwth contests but i am sure you are coming up with some epic ideas)
