Minimum Operations to Transform String

Description

You are given a string s consisting only of lowercase English letters.

You can perform the following operation any number of times (including zero):

-

Choose any character c in the string and replace every occurrence of c with the next lowercase letter in the English alphabet.



Return the minimum number of operations required to transform s into a string consisting of only 'a' characters.

Note: Consider the alphabet as circular, thus 'a' comes after 'z'.