Alphabet

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.

Input

Contains a string s (1 ≤ |s| ≤ 50). It is guaranteed that s consists of lowercase ASCII letters a to z only.

Output

Print the minimum number of letters that must be inserted in order to make the string s alphabetical.

Examples