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 Haskell (GHC 7.10.3) (judge verdict: Accepted)

sol sb sa
    | l == 1        = if sbh == sah then 0 else 1
    | sbh == sah    = 0 + (sol sbt sat)
    | sbh /= sah    = 1 + (sol sbt sat)
    where
        l   = length sa
        sbh = head sb
        sah = head sa
        sbt = tail sb
        sat = tail sa

main=do
    s <- getLine
    let
        n = length s
        sb = take (div n 2) s
        sa = reverse $ drop ((div n 2) + n `mod` 2) s
    print $ if length s /= 1
        then sol sb sa
        else 0