B - Palindrome-philia /

制約

• S は半角英小文字のみから成る文字列
• S の長さは 1 以上 100 以下

入力

S


出力

S を回文にするために必要なハグの最小回数を出力してください。

入力例 1

redcoder


出力例 1

1


たとえば、4 文字目を o に変えて redooder にすることで回文になります。

入力例 2

vvvvvv


出力例 2

0


入力例 3

abcdabc


出力例 3

2


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.

Sample Input 1

redcoder


Sample Output 1

1


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

Sample Input 2

vvvvvv


Sample Output 2

0


We might need no hugs at all.

Sample Input 3

abcdabc


Sample Output 3

2