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 sz(a) int((a).size()) 
#define pb push_back 
#define all(c) (c).begin(),(c).end() 
#define tr(c,i) for(auto i = (c).begin(); i != (c).end(); i++) 
#define present(c,x) ((c).find(x) != (c).end()) 
#define cpresent(c,x) (find(all(c),x) != (c).end())
#define F(i,n) for(int i=0;i<n;i++)
#define MOD 1000000007
#define VE(i,v) for(int i = 0;i < (v).size();i++)

using namespace std;
#define trace(...) cerr<<__FUNCTION__<<":"<<__LINE__<<" "; __f(#__VA_ARGS__, __VA_ARGS__)
template<typename Arg1>
void __f(const char *name, Arg1 &&arg1) {
	cerr<<name<<" : "<<arg1<<endl;
}
template<typename Arg1, typename ... Args>
void __f(const char *names, Arg1 &&arg1, Args &&... args) {
	const char *comma=strchr(names+1,',');
	cerr.write(names,comma-names)<<" : "<<arg1<<" | ";
	__f(comma+1,args...);
}
typedef vector<int> vi; 
typedef vector<vi> vvi; 
typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef long long ll;
typedef unsigned int ui;
typedef vector<ll> vl; 
typedef vector<vl> vvl; 
typedef pair<ll,ll> pll;
typedef vector<pll> vpll; 
 




int main()

{
	std::ios::sync_with_stdio(false);
	cin.tie(NULL);
	int T;
	T=1;
	for(int tc=1; tc<=T;tc++)
	{
		string s;
		cin >> s;
		int lim = sz(s)/2;
		int ans = 0;
		for(int i =0, j = sz(s)-1; i < lim; i++, j--)
			if(s[i]!=s[j])
				ans++;
		cout<<ans<<"\n";
	}
 
 
 
	return 0;
}