You are given a string s of length n containing only the characters 'Q', 'W', 'E', and 'R'.

A string is called balanced if each of these $4$ characters appears exactly n $/$ $4$ times.

Return the minimum length of a contiguous substring that can be replaced with any arbitrary string of the same length to make s balanced. If s is already balanced, return $0$.

Constraints:

• n $==$ s.length

• $4 \leq$ n $\leq 10^5$

• n is a multiple of $4$

• s contains only 'Q', 'W', 'E', and 'R'

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.