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.split('')

size = s.size
answer = 0
count = 0
sr = s.reverse

size.times do |i|

	answer += 1 if sr[i] != s[i]

end

puts answer


=begin
#Chomp無しだと\nが代入される
#解けてない
s = gets.chomp.split('')
st = s.length/2
sr = s.reverse

count = 0
ans = 0
st.times do |i|
	if c[i] != sr[count]
	ans += 1
	count += 1
else
	count += 1
end
end

puts ans
=end