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 CodeForces
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        long n=sc.nextLong();
        int check=0;
        if(n==1||n==2)
        {
            System.out.println("1");
            return;
        }
        for(long i=2;i<=(long)Math.sqrt(n);i++)
        {
            if(n%i==0)
            {
                check++;
                break;
            }
        }
        if(check==1)
        {
            System.out.println(n/2);
        }
        else
        {
            System.out.println("1");
        }
    }
}