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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main()
{
  int i = 0;
  char S[101];
  scanf("%s",&S);
  while (S[i])
    i++;
  //printf("%d\n",i);
  int len = i;
  //printf("i:%d\n",i);
  int k = 0;
  int counter = 0;
  //printf("len/2:%d\n",len/2);
  i -= 1;
  while (k != len / 2)
  {
    if (S[i] != S[k])
    {
      //printf("S[%d]=%c:S[%d]=%c\n",i,S[i],k,S[k]);
      S[i] = S[k];
      counter++;
    }
    i--;
    k++;
  }
  printf("%d",counter);
}