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: Accepted)

function Main(input) {
  input = input.trim();
  input = input.split("");
  var output = input.slice().reverse();
  var count = input.length;
  for(var i=0; i<input.length;i++){
    if(input[i]==output[i]){
      count--;
    }
  }
  console.log(count/2);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));