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: Accepted)

from sys import stdin
a = stdin.readline().rstrip()
a = list(str(a))
cnt = 0
e = 0
if len(a)%2 == 0:
	end = len(a)//2 
else:
	end = len(a)//2 +1

for s,t in zip(a,a[::-1]):
	cnt +=1
	if s != t:
		e += 1
	if cnt == end:
		break

                   
print(e)