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(input) {
    input = input.split("");
    var head = [];
    var tail = [];
    var ans = 0;
    if(input.length%2 == 1){
        ans
    }
    
    for(var i = 0; i < input.length;i++){
        if(i < input.length/2){
            head.push(input[i]);
        }else{
            tail.push(input[i]);
        }
    }
    tail.reverse();
    
    for(var i = 0; i < head.length;i++){
        if(head[i] != tail[i]){
            ans++;
        }
    }
    
    if((head.length%2==0) && (ans != 0)){
        ans--;
    }
console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));