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 Go (1.6) (judge verdict: Accepted)

package main

import "fmt"

func main() {
	var s string
	fmt.Scan(&s)

	res := 0
	for i := 0; i < len(s)/2; i++ {
		if s[i:i+1] != s[len(s)-(i+1):len(s)-i] {
			res++
		}
	}
	fmt.Println(res)
}