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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#define st first
#define nd second
#define mp make_pair
#define pb push_back
#define sol (k+k)
#define sag (k+k+1)
#define orta ((bas+son)/2)
#define ort ((bas+son+1ll)/2ll)
#define coc g[node][i]
#define mod 1000000007
#define inf 1000000009
#define N 1000005
using namespace std;
 
typedef long long ll;
typedef pair < int , int > ii;
 
int t,nf = 0;
string s;
 
int main() {
	
	cin >> s;
	if(s.length() % 2 != 0) t = s.length()/2 + 1;
	else  t = s.length()/2;
	for(int i = 0; i < t; i++)
	{
		if(s[i] != s[s.length() - i - 1])
		{
		    nf++;
		}    
		
	}
	cout << nf;
	
	
	return 0;
}