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.*;
public class prime 
{
   public static void main(String args[])
   {
	   Scanner in=new Scanner(System.in);
	   long n;
	   n=in.nextLong();
	   if(n%2==0)
	   {
		   System.out.println(n/2);
		   System.exit(0);
	   }
	   else
	   {
		   for(int i=3;i<=n;i=i+2)
		   {
			   if(n%i==0 && n-i!=0)
			   {
				   System.out.println((n-i)/2);
				   System.exit(0);
			   }
			   else if(n%i==0 && n==i)
			   {
				   System.out.println("1");
				   System.exit(0);
			   }
		   }
	   }
   }
}
				   