Documentation

Documentation

Description

Coki is a developer who loves doing pranks. The newest one he wants to try is to transform the documentations which his colleagues write into palindromes (from Wikipedia: A palindrome is a word, phrase, number, or other sequence of characters which reads the same backward or forward, such as madam or kayak.).

To do this he follows three rules: 1. He can increase/reduce the value of a letter, e.g. he can change d to e or change e to d (the border cases a to z and z to a are also allowed). 1. Capital letters are treated like non-capital letters, e.g. he can change A to b or change b to A. 1. Special characters such as " " (white space), ",", ".", "!", "?" are disregarded.

Each increase/reduction in the value of a letter is counted as a single operation. Your task is to help Coki find the minimum number of operations required to convert a given documentation text into a palindrome.

Input

  • Input is read from the console
    • On the single line in the console is the string to be converted.

Output

  • Output should be printed on the console
    • A single line denoting the number of minimum operations required to convert the string into a palindrome.

Constraints

  • 1 <= length of string <= 1500000
  • All characters are upper/lower case English letters and the following special characters - " " (white space), ",", ".", "!", "?".
  • Time limit: 0.07s
  • Memory limit: 32 MB

Sample tests

Sample test 1

Input

abc

Output

2

Sample test 2

Input

AZ!x

Output

3

Sample test 3

Input

No x in Nixon

Output

0