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=input()
L=[]
R=[]
count=0
for i in range(len(S)):
    if i<=(len(S)+(2-1))//2-1:
        L.append(S[i])
        R.append(S[-i-1])
for i in range(len(L)):
    if L[i]==R[i]:
        count=count
    else:
        count+=1
print(count)