#include<stdio.h>
#include<string.h>
char a[110];
int main()
{
	scanf("%s",a);
	int i,l=strlen(a),cnt=0;
	for(i=0;i<l/2;i++)
	{
		if(a[i]!=a[l-i-1])cnt++;
	}
	printf("%d\n",cnt);
}
### 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<stdio.h>
#include<string.h>
char a[110];
int main()
{
	scanf("%s",a);
	int i,l=strlen(a),cnt=0;
	for(i=0;i<l/2;i++)
	{
		if(a[i]!=a[l-i-1])cnt++;
	}
	printf("%d\n",cnt);
}
```