Let countUniqueChars(t) denote the number of unique characters in a string t, which is the count of characters that appear exactly $1$ time in t.

Given a string s, return the sum of countUniqueChars(t) for every substring t of s.

Notice that identical substrings appearing at different positions in s are counted separately.

Constraints:

• $1 \leq$ s.length $\leq 10^5$

• s consists of uppercase English letters only.

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.