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>
#include<stdlib.h>

void rev_string(char s[], char t[]){
  //char j[101];
  int i;
  int sum;
  for(i = 0; s[i] != '\0'; i++){
    t[i] = s[i];
    sum++;
  }
  for(i = 0; i <sum; i++){
    s[i] = t[sum - i -1];
  }
}
int main(){
  char s[101];
  char t[101];
  int i , sum= 0;
  scanf("%s", s);
  
  rev_string(s, t);
  for(i = 0; s[i] != '\0'; i++){
    if(s[i] != t[i]){
      sum++;
    }
  }
  printf("%d", sum/2);
  return 0;
}