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;
import java.util.Arrays;
import java.util.Vector;
import java.util.Collections; 

public class Welcomejava { 
    

    public static void main(String[] args) {
        // TODO code application 
        Scanner input = new Scanner(System.in);
        long n , res ;
        boolean falag = false;
        n = input.nextLong();
        if (n % 2 == 0 ) System.out.println(n /2 );
        
        else{
        
            for (int i = 3 ; i <= (int) Math.sqrt(n); i++) {
             
            if (n % i == 0)
            {
             n -= i ;
             falag = true;
             break;
            }
        }
        
        if (falag == true)
        {
            System.out.println((n / 2) + 1 );
        }
        else
            System.out.println(1);
        
        
        }
    

    }
}

