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 Rust (1.42.0) (judge verdict: Accepted)

use text_io::*;
use std::process::exit;
use im_rc::HashMap;
use std::cmp::min;

fn main(){
    let mut a:String = read!();
    let mut v:Vec<char> = a.chars().collect();
    let mut n:usize = 0;
    for i in 0..v.len()/2 {
        if v[i]!=v[v.len()-i-1] {
            n += 1;
        }
    }
    println!("{}",n);
}