#include<stdio.h>
#include<string.h>
int main()
{
	char a[101];
	int i,k,s;
	s=0;
	scanf("%s",a);
	k=strlen(a);
	for(i=0;i<k;i++){
	if(a[i]!=a[k-i-1]) {	s++; }
}
	printf("%d\n",s/2);
	return 0;
}
### 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<stdio.h>
#include<string.h>
int main()
{
	char a[101];
	int i,k,s;
	s=0;
	scanf("%s",a);
	k=strlen(a);
	for(i=0;i<k;i++){
	if(a[i]!=a[k-i-1]) {	s++; }
}
	printf("%d\n",s/2);
	return 0;
}
```