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;

public class Main {

    public static void main(String[] args) {
	// write your code here

        Scanner in = new Scanner(System.in);
        long n = in.nextLong();
        long ans ;
        if (n%2 == 0) ans = n/2;
        else {
            for(long i=3; ;i++){
                if (n%i == 0) {
                    ans = n/i;
                    break;
                }
            }
        }
        System.out.println(ans);

    /*
        int t;
        Scanner in = new Scanner(System.in);
        t = in.nextInt();
        double d;
        for(int i=0;i<t;i++){
            d = in.nextDouble();
            double delta = d*d+4*d ;
            double x1,x2;
            x1 = (d-delta)/2;
            x2 = (d+delta)/2;
            if (d >0) System.out.println("N");
            else {
                System.out.println("Y "+x2+" "+x1);
            }
        }
        */

    }
}
