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