Problem:
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

Solution in Scala (2.11.7) (judge verdict: Accepted)

object Main extends App {
  val target = io.StdIn.readLine()
  
  val (former, latter) = if (target.length % 2 == 0)
  	target.splitAt(target.length / 2)
  else
  	(target.substring(0, target.length / 2), target.substring(target.length / 2 + 1))
  
  val answer = former.zip(latter.reverse).count(pair => pair._1 != pair._2)
  
  println(answer)
}