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++ (GCC 9.2.1) (judge verdict: Accepted)

#if __has_include("debug.h")
    #include "debug.h"
#else  
#include <bits/stdc++.h>
using namespace std;
#define d(...) 2;
#endif

#define int long long int
#define ld long double

#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl "\n"      

#define all(c) (c).begin(),(c).end()
#define rall(c) (c).rbegin(),(c).rend()
#define ff first
#define ss second
#define eps 1e-10
#define PI acos(-1LL)

#define gcd(a,b)            __gcd((a),(b))
#define lcm(a,b)            ((a*b)/gcd(a,b))

void solve();

int32_t main()
{
    #ifdef DEBUG
	freopen("input.txt","r",stdin);
	freopen("output.txt","w",stdout);
    #endif 

    fast
    
    int t = 1;
	// cin>>t;
	
	while(t--)
	    solve();
	return 0;  
}

void solve()
{
	int i,j;
	string s;
	cin>>s;

	int l=s.length(),cnt=0;

	for(i=0;i<s.length()/2;i++)
	{
		if(s[i]!=s[l-i-1])
		{
			cnt++;
		}
	}
	cout<<cnt<<endl;

}