A string of lowercase letters is called alphabetical if deleting zero or more of its letters can result in the alphabet string "abcdefghijklmnopqrstuvwxyz".
Given a string s, determine the minimum number of letters to insert anywhere in the string to make it alphabetical.
Contains a string s (1 ≤ |s| ≤ 50). It is guaranteed that s consists of lowercase ASCII letters a to z only.
Print the minimum number of letters that must be inserted in order to make the string s alphabetical.