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

int main(){
  string S;
  int i,cnt=0;
  cin >> S;

  for(i=0;i<S.size()/2;i++)
  if(S.at(i)!=S.at(S.size()-1-i))
  cnt++;

  cout << cnt << endl;

}
### Prompt

Develop a solution in Cpp to the problem described below:

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;
  int i,cnt=0;
  cin >> S;

  for(i=0;i<S.size()/2;i++)
  if(S.at(i)!=S.at(S.size()-1-i))
  cnt++;

  cout << cnt << endl;

}
```