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>
using namespace std;
typedef long long lo;
typedef pair<lo,lo> ll;//pair
typedef vector<lo> vl;  //vector of long
typedef vector<ll > vll;   //vector of pair
typedef priority_queue<lo>p_q;
#define mp(a,b) make_pair((a),(b))
#define REP(a,b) for(lo i=(a);i<(b);i++)//no need to declare variable i
#define REPE(a,b,c,d) REP(a,b)for(lo j=(c);j<(d);j++)//no need to declare vaiables i,j
#define REPV(a,b,c) for((a)=b;(a)<(c);(a)++)//a is the variable
#define IREP(a,b) for(lo i=(a);i>=(b);i--)
#define IREPV(a,b,c) for((a)=b;(a)>=(c);(a)--)
#define all(v) (v).begin(),(v).end()
#define TRvl(c) for (vl::iterator it = (c).begin(); it != (c).end(); it++)
#define TRvll(c) for (vll::iterator it = (c).begin(); it != (c).end(); it++)
#define gc getchar_unlocked
#define pc putchar_unlocked3
#define pb(a) push_back((a))
 
 
void solve()
{
    string str;
    cin>>str;
    int ans=  0;
    int n = str.length();
    for(int i=0;i<n/2;i++)
    {
        if(str[i]!=str[n-1-i])ans++;
    }
    cout<<ans<<endl;

}
 
int main()
{
    /*
    #ifndef ONLINE_JUDGE
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    #endif 
    */
        ll t;
    //cin>>t;
    //while(t--)
        solve();
}