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[])
    {
        Scanner in=new Scanner(System.in);
        long n,i,a,c=0;
        n=in.nextLong();
        boolean b=false;
        if(n==0)
        {
            System.exit(0);
        }
        for(i=2;i<n;i++)
        {
            if(n%i==0)
            {
                if(i==2)
                {
                    n=n-i;
                    i=2;
                }
            for(a=2;a<i;a++)
            {
                if(i%a==0)
                {
                    b=true;
                }
            }
            if(b==true)
            {
                c=c+1;
                n=n-i;
                i=2;
            }
            }
        }
        System.out.println(c);
    }
}