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

int main() {
	string S;
	cin >>S;
	int n,c;
	n=S.length();
	c=0;
	for(int i=0;i<n/2;i++){
		if(S.at(i)!=S.at(n-i-1)){
			c++;
		}
	}
	cout <<c;
}
### 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;

int main() {
	string S;
	cin >>S;
	int n,c;
	n=S.length();
	c=0;
	for(int i=0;i<n/2;i++){
		if(S.at(i)!=S.at(n-i-1)){
			c++;
		}
	}
	cout <<c;
}
```