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