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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

"use strict";

function main(input) {
  input = input.trim().split("");
  let ans = 0;
  for (let i = 0; i < Math.floor(input.length / 2); i++) {
    if (input[i] !== input[input.length - (i + 1)]) {
      ans++;
    }
  }
  console.log(ans);
}

main(require("fs").readFileSync("/dev/stdin", "utf-8"));