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 <iostream>
#include <map>
#include <string>
#include <utility>
#include <list>
#include <math.h>
#include <vector>
#include <algorithm>
#include<iomanip>
#include <unordered_map> 
#include <queue>
 
using namespace std;
typedef long long ll;
typedef pair<int, int> pp;
 
#define MOD 1000000007
 
 
int main() {
  
  string S;
  
  cin >> S;
  
  int len = S.length();
  int cnt = 0;
  
  for (int i = 0; i < (len / 2); i++) {
    if (S[i] == S[len - i - 1]) {
      
    }
    else {
       cnt++;
    }
  }
  
  cout << cnt;
 
  //for float, double precision
  //cout << std::fixed << setprecision(15);
  return 0;
 
}