2981. Find Longest Special Substring That Occurs Thrice I

You are given a string s that consists of lowercase English letters. A string is called special if it is made up of only a single character. For example, the string "abc" is not special, whereas the strings "ddd", "zz", and "f" are special. Return the length of the longest special substring of s which occurs at least thrice, or -1 if no special substring occurs at least thrice. A substring is a