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)

x = gets.chomp.split("")

left_half = left_half = x[0..x.size/2 - 1]
mid = 0
if x.size.even?
  mid = x.size/2 - 1 + 1
else
  mid = x.size/2 - 1 + 2
end
right_half = x[mid..-1].reverse

res = 0
left_half.each_with_index do |i, idx|
  res += 1 unless right_half[idx] == i
end

puts res