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("")

mid = (s.length-1) / 2

front = Array.new(mid)
back = Array.new(mid)

for i in 0..mid do
    front[i] = s[i]
end

for i in mid+1..s.length-1 do
    back[s.length - 1 - i] = s[i]
end

if(front.length != back.length)
    front.pop
end

tigau = 0

for i in 0..front.length-1 do
    if(front[i] != back[i])
        tigau += 1
    end
end

puts tigau