B - Palindrome-philia

Score : $200$ points

Problem Statement

Takahashi loves palindromes. Non-palindromic strings are unacceptable to him. Each time he hugs a string, he can change one of its characters to any character of his choice.

Given is a string $S$. Find the minimum number of hugs needed to make $S$ palindromic.

Constraints

• $S$ is a string consisting of lowercase English letters.
• The length of $S$ is between $1$ and $100$ (inclusive).

Input

Input is given from Standard Input in the following format:

$S$

Output

Print the minimum number of hugs needed to make $S$ palindromic.

redcoder

1

For example, we can change the fourth character to o and get a palindrome redooder.

vvvvvv

0

We might need no hugs at all.

abcdabc

2