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 Helloworld {

	public static void main(String[] args) {
		Scanner s=new Scanner(System.in);
		long n, a=0;
		n=s.nextLong();
		if(n%2!=0)
	for(long i=3;i<=n;i++)
		if(f(i) && n%i==0)
		{
			n-=i;
			a++;
			break;
		}
			a+=n/2;
			System.out.print(a);
				}
			

static boolean f(long d)
{
	for(long i=2;i<d;i++) if(d%i==0) return true;
	return false;
}
			}
	
	

