Longest Substring With At Least K Repeating Characters

Implement solve for Longest Substring With At Least K Repeating Characters. Return the required output for the provided arguments.

Given a string s and an integer k, find the length of the longest substring of s where each character appears at least k times.

Examples
Input: ["aaabb",3]
Output: 3
Hints

Longest Substring With At Least K Repeating Characters

Implement `solve` for **Longest Substring With At Least K Repeating Characters**. Return the required output for the provided arguments.