You are given a string s.

Initially, all indices in the string are unmarked, and the total score is $0$.

The mirror of a lowercase English letter is the letter at the same distance from the opposite end of the alphabet. For instance, the mirror of 'a' is 'z', the mirror of 'b' is 'y', and the mirror of 'c' is 'x'.

Traverse the string from left to right using an index i from $0$ to s.length $- 1$:

1. Find the closest unmarked index j such that j $<$ i and s[j] is the mirror character of s[i].

2. If such an index j exists, mark both i and j, and add i $-$ j to the total score.

3. If no such index exists, move to the next index without modifying the score.

Return the total score after processing all indices.

Constraints:

• $1 \leq$ s.length $\leq 10^5$

• s consists only of lowercase English letters.

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.