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)

s = gets.chomp
cnt=0
if s.length%2==0
  a=s[0..(s.length/2-1)]
  b=s[(s.length/2)..-1].reverse

  a.chars.each_with_index do |s,i|
    cnt+=1 if a[i] == b[i]
  end
  puts a.length-cnt

else
  c=s[0..(s.length/2-1)]
  d=s[(s.length/2+1)..-1].reverse

  c.chars.each_with_index do |s,i|
    cnt+=1 if c[i] == d[i]
  end
  puts c.length-cnt
end