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

signed main(){
  string s;cin>>s;
  int ans=0;
  int n=s.size();
  for(int i=0;i<n/2;i++){
    if(s[i]!=s[n-i-1])ans++;
  }
  cout<<ans<<endl;
}
### Prompt

Construct a CPP code solution to the problem outlined:

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;

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