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>
#include<iostream>
#include<cmath>
#include<cstdio>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<utility>
#include<algorithm>
#include<cstring>
#include<sstream>
#include <iomanip>

using namespace std;

typedef long long ll ;
typedef double db;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef vector< pair<int,int> > vii;
const double pi = 2*acos(0) ;

#define pf		  	printf
#define sf			  scanf
#define pb(a)         push_back(a)
#define mp			make_pair
#define fi			 first
#define se			 second
#define for0(i,n)        for(int i=0;i<n;i++)
#define for1(i,n)        for(int i=1;i<=n;i++)
#define forab(i,a,b)       for(int i=a;i<=b;i++)
#define lcm(a, b)     ((a)*((b)/gcd(a,b)))
#define sq(a)		   (a)*(a)
#define nw				"\n"
#define abs(x)		fabs(x)
#define pcase(z,x)    cout<<"Case "<<z<<": "<<x<<"\n"

int main()
{
	int n,c=0;
	string s;
	cin>>s;
	n = s.size();
	for0(i,n/2){
		if(s[i]!=s[n-i-1]) c++;
		}
	cout<<c<<nw;
	return 0;
}