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)

s=str(input())
n=len(s)
l=list(s)
if(n%2==0):
  p=l[0:n//2]
  q=l[n//2:]
else:
  p=l[:n//2]
  q=l[(n//2+1):]
q.reverse()
cnt=0
m=[x for x in range(len(p))]
for num in m:
  if(p[num]!=q[num]):
    cnt+=1
print(cnt)