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: Runtime Error)

#include<stdio.h>
#include<string.h>
#include<stdio.h>

int main(){
  char str1[100] = {};
  char str2[100] = {};
  int i,num=0;
  int loopnum;
  
  if(scanf("%s",str1)<1)
    exit(1);
  
  strcpy(str2,str1);
  if(strlen(str1) % 2 == 0)
    loopnum = strlen(str1)/2;
  else
    loopnum = strlen(str1)/2 + 1;
  
  for(i = 0; i < loopnum; i++){
    if(str1[i] != str2[strlen(str1) - 1 - i]){
      num++;
    }
  }
  
  printf("%d",num);
  
  return 0;
}