#include<iostream>
#include<string>
using namespace std;
int main()
{ 
	string str;
	cin>>str;
	int l=str.length();
	int num=0;
	for(int i=(l+1)/2-1;i>=0;i--)
	if(str[i]!=str[l-1-i]) num++;
	cout<<num;
}
### 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>
#include<string>
using namespace std;
int main()
{ 
	string str;
	cin>>str;
	int l=str.length();
	int num=0;
	for(int i=(l+1)/2-1;i>=0;i--)
	if(str[i]!=str[l-1-i]) num++;
	cout<<num;
}
```