Minimum Operations to Make Character Frequencies Equal

Given a lowercase string s, compute the minimum number of operations (delete, insert, or change a character to its next alphabet letter — no wrap from 'z' to 'a') to transform s into a "good" string where every character present occurs the same number of times. The core challenge is choosing the final set of distinct letters and target frequency while respecting that character changes can only move forward in the alphabet and length can be adjusted by inserts/deletes.