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)

n = gets.chomp
n = n.split("")
l = n.count/2
if n.count%2==1
  k = n[0..l-1]
  m = n[l+1..n.count-1].reverse!
  count = 0
  i = 0
  for i in 0..l-1 do
    if k[i] != m[i]
      count += 1
    end
    i += 1
  end
  p count
else
  k = n[0..l-1]
  m = n[l..n.count-1].reverse!
  count = 0
  i = 0
  for i in 0..l-1 do
    if k[i] != m[i]
      count += 1
    end
    i += 1
  end
  p count
end