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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;
import java.lang.*;
import java.io.*;

public class Main{
    public static void main(String[] args) throws IOException{
        FastReader in = new FastReader();
        FastWriter out = new FastWriter();
        String a = in.nextLine();
        int ans = 0;
        for (int i = 0; i < a.length()/2; i++){
            if (a.charAt(i) != a.charAt(a.length()-(i+1))){
                ans++;
            }
        }
        out.pl(ans);
        out.close();
    }
}
class FastReader{ 
    BufferedReader br; 
    StringTokenizer st; 
    public FastReader() { 
        br = new BufferedReader(new InputStreamReader(System.in)); 
    } 
    String next(){ 
        while (st == null || !st.hasMoreElements()) { 
            try{ 
                st = new StringTokenizer(br.readLine()); 
            }catch (IOException  e){ 
                e.printStackTrace(); 
            } 
        } 
        return st.nextToken(); 
    } 
    int nextInt(){ 
        return Integer.parseInt(next()); 
    } 
    long nextLong(){ 
        return Long.parseLong(next()); 
    } 
    double nextDouble(){ 
      return Double.parseDouble(next()); 
    } 
    String nextLine(){ 
        String str = ""; 
        try{ 
            str = br.readLine(); 
        } 
        catch (IOException e){ 
            e.printStackTrace(); 
        } 
        return str; 
    } 
}
class FastWriter{
    PrintWriter out;
    FastWriter(){
        out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
	out.flush();
    }
    void pl(Object o){
        out.write(o.toString());
	    out.write("\n");
        out.flush();
    }
    void pl(){
        out.write("\n");
    }
    void p(Object o){
        out.write(o.toString());
    }
    void close(){
        out.flush();
        out.close();
    }  
}