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.split('')

first = []
second = []

if s.count%2 == 0
	(0..s.count-1).each do |i|
		if i < s.count/2
			first << s[i]
		else
			second << s[i]
		end
	end
else
	(0..s.count-1).each do |i|
		if i < s.count/2
			first << s[i]
		elsif i == s.count/2
			first << s[i]
			second << s[i]
		else
			second << s[i]
		end
	end
end

i = 0
count = 0

second.reverse!

while i < first.count
	if first[i] != second[i]
		count += 1
	end
	i += 1
end

puts count