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)

// Vicfred
// https://atcoder.jp/contests/abc147/tasks/abc147_b
// string manipulation
use std::io;

fn main() {
    let mut s = String::new();

    io::stdin()
        .read_line(&mut s)
        .unwrap();

    let s = s.trim();

    let n = s.len();
    let s: Vec<char> = s.chars().collect();

    let mut answer = 0;

    for i in 0..n as usize {
        if s[i] != s[n-i-1] {
            answer += 1;
        }
    }

    println!("{}", answer/2);

}