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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

import java.util.*;
public class Main {
    /**
     * @param args
     */
    public static void main(final String[] args) {
 		Scanner sc = new Scanner(System.in);
 		final String aStr = sc.next();;
 
        /** 不一致件数カウント */
        int aCount = 0;
        /** インクリメント変数 */
        int aI = 0;
 
        while (aI * 2 < aStr.length()) {
            if (aStr.charAt(aI) == aStr.charAt(aStr.length() - aI - 1)) {
                // 何もしない
            } else {
                aCount++;
            }
            aI++;
        }
        System.out.println(aCount);
    }
}