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 Ruby (2.3.3) (judge verdict: Wrong Answer)

str = gets.split("")

left = 0
right = str.size-1
ans = 0

if str.size%2 == 0
    while left+1 != right
        if str[left] == str[right]
        else
            ans += 1
        end
        left += 1
        right -= 1
    end
    
    if str[left] == str[right]
        puts ans
    else
        puts ans+1
    end
else
    while left != right
        if str[left] == str[right]
        else
            ans += 1
        end
        left += 1
        right -= 1
    end
    
    if str[left] == str[right]
        puts ans
    else
        puts ans+1
    end
end