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 v5.12) (judge verdict: Wrong Answer)

function Main(s) {
  var answer = 0;

  const half = Math.ceil(s.length / 2);
  for (var i = half; i < s.length; i++) {
    if (s[s.length - i - 1] !== s[i]) {
      answer++;
    }
  }

  //出力
  console.log(answer);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));