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 (1.15.1) (judge verdict: Accepted)

fn main() {
    let stdin = std::io::stdin();
    let mut buf = String::new();

    stdin.read_line(&mut buf).unwrap();
    let s_arr: Vec<char> = buf.trim().chars().collect();

    let len = s_arr.len();
    let mut ans: usize = 0;
    for i in 0..len/2 {
        if s_arr[i] != s_arr[len-1-i] {
            ans += 1;
        }
    }
    println!("{}", ans);
}