#include<bits/stdc++.h>
using namespace std;
int main(){
  string s; cin >> s;
  int cnt = 0;
  for(int i = 0; i < s.size()/2; i++){
    if(s.at(i) != s.at(s.size() - i - 1)) cnt++;
  }
  cout << cnt;

}
### 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 cnt = 0;
  for(int i = 0; i < s.size()/2; i++){
    if(s.at(i) != s.at(s.size() - i - 1)) cnt++;
  }
  cout << cnt;

}
```