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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#define ll long long
#define rgi register int
#define pii pair<int,int>
#define mkp make_pair
#define fi first
#define se second
#define pb push_back
#define filein(x) freopen(x,"r",stdin)
#define fileout(x) freopen(x,"w",stdout)
using namespace std;
int n,ans;
string s;
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	cin>>s;
	n=s.size();
	rgi i=0,j=n-1;
	while(i<j)
	{
		if(s[i]!=s[j])
			++ans;
		++i,--j;
	}
	cout<<ans<<endl;
	return 0;
}