#include<bits/stdc++.h>
using namespace std;
string s;
int ans;
int main() {
	cin>>s;
	for(int i=0;i<s.length();i++) if(s[i]!=s[s.length()-1-i]) ans++;
	cout<<ans/2;
	return 0;
}
### Prompt

Please create a solution in Cpp 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;
string s;
int ans;
int main() {
	cin>>s;
	for(int i=0;i<s.length();i++) if(s[i]!=s[s.length()-1-i]) ans++;
	cout<<ans/2;
	return 0;
}
```