You are given an integer number n. The following algorithm is applied to it:

  1. if n = 0, then end algorithm; 
  2. find the smallest prime divisor d of n; 
  3. subtract d from n and go to step 1. 



Determine the number of subtrations the algorithm will make.

Input

The only line contains a single integer n (2 ≤ n ≤ 10^{10}).

Output

Print a single integer — the number of subtractions the algorithm will make.

Examples

Input


5


Output


1


Input


4


Output


2

Note

In the first example 5 is the smallest prime divisor, thus it gets subtracted right away to make a 0.

In the second example 2 is the smallest prime divisor at both steps.


import java.util.Scanner;

/**
 *
 * @author Ahmed
 */


public class CF {

    /**
     * @param args the command line arguments
     */
    

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        long n = input.nextLong();
        if (n % 2 == 0){
            System.out.println(n/2);
        }else{
            boolean prime = true;
            for (long i = 3; i*i <= n; i++) {
                if (n % i == 0){
                    prime = false;
                    n -= i;
                    break;
                }
                    
            }
            if (prime)
                System.out.println(1);
            else
                System.out.println(n/2 + 1);
        }
    }

}
