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 INF 9223372036854775807LL
#define inf 1000000007
#define SYOU(x) setprecision(x+1)
#define abs(x,y) (max(x,y)-min(x,y))
#define lol long long
#define mp make_pair
#define fi first
#define se second
using namespace std;
lol a,b,x=0,y;
signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int c,d=0,e=0,f=0,g=1,h=0;
    string s;
    cin >>s;
    a=s.size()/2;
    for(int n=0;n<a;n++){
      if(s[n]!=s[s.size()-1-n]) d++;
    }
    cout <<d<<'\n';
    return (0);
}