#include<bits/stdc++.h>
using namespace std;

int main(){ 
string s;
cin>>s;
int A=0;
size_t n = s.length();
for(int i=0; i<n; i++){
if(s[i]!=s[n-1-i]){
A++;
}
}
cout<<A/2<<endl;
}

### Prompt

Your challenge is to write a CPP solution to the following problem:

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.

Examples

Input

redcoder


Output

1


Input

vvvvvv


Output

0


Input

abcdabc


Output

2

### Response

```cpp
#include<bits/stdc++.h>
using namespace std;

int main(){ 
string s;
cin>>s;
int A=0;
size_t n = s.length();
for(int i=0; i<n; i++){
if(s[i]!=s[n-1-i]){
A++;
}
}
cout<<A/2<<endl;
}

```