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 subtraction {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in=new Scanner(System.in);
		long n=in.nextLong();
		boolean b=true;
		if(n%10==7)
		{
			System.out.println("NO");
			System.exit(0);
		}
		if(n%2==0)
		{
			System.out.println(n/2);
		}
		else if(n%2!=0)
		{
			for(long i=3;i<=n;i=i+2)
			{
				if(n%i==0)
				{
					for(long a=2;a<i;a++)
					{
						if(i%a==0)
						{
							b=false;
						}
					}
					if(b==true)
					{
						System.out.println(1+(n-i)/2);
						System.exit(0);
					}
				}
			}
		}
	}
}