#include<iostream>
using namespace std;
int main(){
 int n,i,ans=0;
string s;
   cin >> s;
n=s.length();
for(i=0;i*2<n;i++) if(s[i]!=s[n-i-1]) ans++;
cout << ans;
  return 0;
}
### 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<iostream>
using namespace std;
int main(){
 int n,i,ans=0;
string s;
   cin >> s;
n=s.length();
for(i=0;i*2<n;i++) if(s[i]!=s[n-i-1]) ans++;
cout << ans;
  return 0;
}
```