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.io.*;
import java.util.*;

public class DivisorSubtraction {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		long n = Long.parseLong(scan.nextLine());
		scan.close();

		long count = 0;
		long divisor = -1;
		
		for(long i = 2; i <= Math.sqrt(n); ++i) {
			if(n%i==0) {
				divisor = i;
				break;
			}
		}
		
		if(divisor==-1) {
			System.out.println("1");
		}
		else if(n%2==0){
			System.out.println(n/divisor);
		}
		else {
			System.out.println((n-divisor)/2 + 1);
		}
	}

}
