I am working on Segment Trees, and more recently with this implementation by [user:AI.Cash]

He brings up this problem but even with the segment tree already built (I assume it stores the number of 'c's in a given range) I don't know how to answer the queries in O(logn).

I would appreciate some help with that problem, and recommendations for other good segment tree problems. Preferably on Codeforces (there is no segTree tag; data structures is the closest but it's no guarantee).

Thanks and have a good day!