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 JavaScript (node.js v5.12) (judge verdict: Runtime Error)

def minReplacements(original, palindrome, m, n):
    # base case:  we're finished processing either string so we're done
    if (m == 0):  # done processing original string
        return n  # return the number of characters left in palindrome
    if (n == 0):  # done processing palindrome
        return m  # return the number of characters left in the original string

    # The characters in the string match so find out how many edits are
    # required for the remaining characters in the strings.
    if (original[m] == palindrome[n]):
        return minReplacements(origininal, palindrome, m-1, n-1)

    # Recurse on editing a character in the original string
    # with a character in the palindrome string
    return 1 + min(minReplacements(origininal, palindrome, m, n-1),   # insert character
                   minReplacements(origininal, palindrome, m-1, n-1), # replace character
                   minReplacements(origininal, palindrome, m-1, n))   # delete character