8.1 How many ACs?
(RankList for this Question)
Score: 30pts
Time Limit: 1.00 sec
You are given a string $$s$$ of length $$L$$ containing alphabets $$A$$ and $$C$$. You need to print the count of unique subsequences of $$AC$$ in string $$s$$. Two subsequences are said to be unique if the indices of either character $$A$$ or character $$C$$ or both differ.<br>

A subsequence is a sequence that can be derived from the given sequence of string by deleting zero or more characters without changing the order of the remaining elements.

Constraints
$$2 \leq L \leq 100000$$
String $$s$$ contains only characters ‘A’ and ‘C’.

Input Format
$$L$$
$$s$$

Output Format
An integer, x, denoting the total number of subsequences of $$AC$$ in string $$s$$.

Example 1
Input:
7
CACCAAC

Output:
5

Explanation:
Explanation -
If we consider the indexing to be done using 0-based indexing, then the index pairs for ‘A’ and ‘C’ are - (1,2), (1,3), (1,6), (4,6), (5,6).

Example 2
Input:
7
ACACACC

Output:
9

Explanation:
The index pairs for ‘A’ and ‘C’ are - (1,2), (1,4), (1,6), (1,7), (3,4), (3,6), (3,7), (5,6), (5,7)