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

int main () {
  string s;
  cin >> s;
  int ans = 0, N = s.length();
  for (int i=0;i<N;++i)
    if (s[i] != s[N-1-i]) ans++;
  printf("%d\n",ans/2);
}

### Prompt

Your task is to create a cpp solution to 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 <bits/stdc++.h>
using namespace std;

int main () {
  string s;
  cin >> s;
  int ans = 0, N = s.length();
  for (int i=0;i<N;++i)
    if (s[i] != s[N-1-i]) ans++;
  printf("%d\n",ans/2);
}

```