#include <iostream>
using namespace std;

int main() {
	string S;
	cin >> S;
	int count=0;
	for (int i=0; i<S.size()/2; i++){
	    if (S.at(i)!=S.at(S.size()-i-1)) count++;
	}
	cout << count << endl;
}

### Prompt

In cpp, your task is to solve 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 <iostream>
using namespace std;

int main() {
	string S;
	cin >> S;
	int count=0;
	for (int i=0; i<S.size()/2; i++){
	    if (S.at(i)!=S.at(S.size()-i-1)) count++;
	}
	cout << count << endl;
}

```