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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