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.*;

public class Main{

    static long gcd(long a,long b){
        if(b==0)return a;
        return gcd(b,a%b);
    }

    static long lcm(long a,long b){
        return a/gcd(a,b)*b;
    }
    public static void main(String[] srgs){
        Scanner sc=new Scanner(System.in);

        String s=sc.next();
        int c=0;
        for(int i=0;i<s.length();i++)if(s.charAt(i)!=s.charAt(s.length()-1-i))c+=1;
        System.out.println(c/2);

    }
}