Problem:
Score : 200 points

Problem Statement

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.

Sample Input 1

redcoder

Sample Output 1

1

For example, we can change the fourth character to o and get a palindrome redooder.

Sample Input 2

vvvvvv

Sample Output 2

0

We might need no hugs at all.

Sample Input 3

abcdabc

Sample Output 3

2

Solution in C (Clang 3.8.0) (judge verdict: Accepted)

#include<stdio.h>
int main(){
  int i,c;
  int k = 0;
  char S[200];
  scanf("%s",S);
  for(i=0;S[i]!='\0';i++);
    for(c=0;c<i/2;c++){
      if(S[c]!=S[i-1-c])++k;
    }
  printf("%d",k);
}