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
reverse_s = s.reverse
ans = 0
for i in (0..(s.length / 2 - 1)) do
  # puts("s[" + i.to_s + "] = " + s[i])
  # puts("reverse_s[" + i.to_s + "] = " + reverse_s[i])
  if s[i] != reverse_s[i]
    ans += 1
  end
end
puts(ans)