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("")

s1, s2 = []

if s.size % 2 == 0 then
	s1 = s[0 ... s.size / 2]
	s2 = s[s.size / 2 .. -1]
else
	s1 = s[0 ... s.size / 2]
	s2 = s[s.size / 2 + 1 .. -1]
end

s2 = s2.reverse

count = 0

s1.each_with_index{ |ss, i|
	if ss != s2[i] then
		count += 1
	end
}

puts count