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>
#include<stdio.h>
void f(char a[],char b[]) {
    int i,j;
    for(i=0; a[i]!='\0'; i++);
    i--;
    for(j=0; j<=i; j++)
        b[j]=a[i-j];
        b[j]='\0';
}
int main()
{
    char a[1000],b[100];
    gets(a);
    f(a,b);
    int t=strlen(a);
    int i,s=0;
    for(i=0;a[i]!='\0';i++)
    if(a[i]!=b[i])
    s++;
    if(t%2==0)
    s=s/2;
    else
    s=(s+1)/2;
    printf("%d",s);
    return 0;
}