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)

int = gets.to_s
int_size = int.length

if int_size.even?
  half_size = (int.length / 2)
else
  half_size = (int.length - 1) / 2
end
 
front = int[0, half_size]

if int_size.even?
  back = int[half_size, int_size]
else
  back = int[half_size + 1, int_size]
end

counts = 0
 
half_size.times do |n|
  if front[n - 1] != back.reverse[n - 1]
    counts += 1
  end
end
 
p counts