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 (2.7.6) (judge verdict: Runtime Error)

a = input()
a = list(a)
b = len(a)
c = b / 2
d = []
for i in range(0,c):
    d.append(a[i])
e = a[::-1]
f = []
for g in range(0,c):
    f.append(e[g])
answer = 0
for h in range(0,c):
    if d[h] != f[h]:
        answer += 1
print(answer)