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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Dynamic;
using System.Linq;
using System.Numerics;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;

namespace atcorder
{
    class Program
    {
        static void Main(string[] args)
        {
            string S = Console.ReadLine();
            int len = S.Length;
            int count = 0;
            for(int i = 0; i < len / 2; i++)
            {
                if(S[i] != S[len - i - 1])
                {
                    count++;
                }
            }
            Console.WriteLine(count);
        }
    }
}


//文字配列の取得
//string[] strArray = Console.ReadLine().Split(' ').ToArray();
//string S = strArray[0];
//string T = strArray[1];

//文字列の取得
//string s = Console.ReadLine();

//数字配列の取得
//int[] intArray = Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray();
//int H = intArray[0];
//int W = intArray[1];

//数字の取得
//int N = int.Parse(Console.ReadLine());

//リスト型(int)の取得
//List<int> A = new List<int>(Console.ReadLine().Split(' ').Select(i => int.Parse(i)).ToArray());

//出力
//Console.WriteLine(ans);
//Console.WriteLine("Yes");
//Console.WriteLine("No");
//Console.WriteLine(cnt);