Hi~

To be able to get the hell out of this grey color, i'm learning new data structures. One of those is Fenwick Tree. By copying code of others on the internet, i'm now able to perform some basic operations such as min / max/ sum on a specific interval. Now here come a new problem, how to find the maximum X * f(X) on range [0, r], f(X) here denotes the occurrences of X within that interval. Thank you all, I much appreciate it!