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.
/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Main
{


         
	public static void main (String[] args) throws java.lang.Exception
	{
            Scanner in=new Scanner(System.in);
            long n=in.nextLong();
            
            if(n==0)System.out.println("0");
            else if(isPrime(n))System.out.println("1");
            else
            {
                long sPrime=0;
                for(long i=2;i*i<=n;i++)
                {
                    if((n%i)==0)
                    {
                        sPrime=i;
                        break;
                    }
                }
                System.out.println(n/sPrime);
            }


    }

    public static boolean isPrime(long n)
    {
        // boolean result = false;

        for(long i=2;i*i<=n;i++)
        {
            if((n%i)==0) return false;
        }
        // System.out.println(result);
        return true;
    }

}
