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 Python (3.4.3) (judge verdict: Wrong Answer)


# coding: utf-8
# Your code here!
import sys
read = sys.stdin.read
readline = sys.stdin.readline 
readlines = sys.stdin.readlines

#n = int(input())
#a = [int(i) for i in readline().split()]


s = input()
ans = 0
n = len(s)
for i in range(n):
    if s[i] != s[-i]: ans += 1




print(ans//2)