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: Runtime Error)

`use strict`

function Main(input) {
  const a = input.trim().split('')
  const N = a.length

  if(N === 1) {
    console.log(0)
    return
  }

  let c = 0
  for(let i = 0; i < Math.floor(N/2); ++i) {
    const t = a[i]
    const l = a[N - 1 - i]
    if (t !== l) c++
  }
  console.log(c)
  
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));