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;

namespace test2 {

    public class Program {

        public static void Main(string[] args) {

            var s = Console.ReadLine();

            var res = 0;
            var n = s.Length;

            for(int i = 0; i < n; i++) {

                if(s[i] != s[n - 1 - i]) {

                    res++;

                }

            }

            Console.WriteLine(res / 2);

        }

    }

}