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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main{
	public static void main(String args[]){
		// 入力読み込み
		Scanner scan = new Scanner(System.in);
		String S = scan.next();
		// 入力終わり
		scan.close();

		// 文字列の数を取得
		int Slength = S.length();

		// 文字列を一文字ずつの配列に置き換え
		char[] tmp = S.toCharArray();

		// 回文にするために必要なハグの回数をカウントする変数
		int C = 0;

		// 両端から文字が一致しているか確認していく
		for(int i=0; i<Slength/2; i++){
			// 一致していない場合、カウント用変数をインクリメントする
			if(tmp[i]!=tmp[Slength-i-1]){
				C++;
			}
		}
		System.out.println(C);
	}
}