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>
using namespace std;
#define ll long long
inline int read(){
    int num=0,w=0;
    char ch=0;
    while(!isdigit(ch)){
        w|=ch=='-';
        ch=getchar();
    }
    while(isdigit(ch)){
        num=(num<<3)+(num<<1)+(ch^48);
        ch=getchar();
    }
    return w?-num:num;
}

//快速写
inline void write(int x)
{
    if(x<0){
        putchar('-');
        x=-x;
    }
    if(x>9)write(x/10);
    putchar(x%10+'0');
}

int arr[1000];
int main()
{
   string s ;
   cin >>s;
   int len = s.size();
   int len1 = len-1 ;
   int sum =0 ;
   if(len%2==1)len++;
   for(int i=0;i<(len)/2;i++){
       if(s[i]!=s[len1]){
           sum++;
          // cout<<i<<endl;
           len1--;
       }else {
           len1--;
       }
   }
   cout<<sum<<endl;
    return 0;
}