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 Fortran (gfortran v4.8.4) (judge verdict: Accepted)

program speedrun
    implicit none
    character(100)::S
    integer::ANS=0,L
    integer::i
    read*,S
    L=len_trim(S)
    do i=1,L/2
        if(S(i:i)/=S(L-i+1:L-i+1))ANS=ANS+1
    end do
    print"(i0)",ANS
end program speedrun