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: Accepted)

s = gets.chomp

s_size = s.size

if s_size.odd?
  ary1 = s.slice(0, s_size / 2).split('')
  # m = s.slice(s / 2)
  ary2 = s.slice(s_size / 2 + 1, s_size).split('')
else
  ary1 = s.slice(0, s_size / 2).split('')
  # m = nil
  ary2 = s.slice(s_size / 2, s_size).split('')
end

ary2 = ary2.reverse

puts ary1.each_with_index.count { |s1, i| s1 != ary2[i] }