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 Codechef
{
	static ArrayList<Integer> arr[];
	static boolean visited[];
	static int node=0;
	public static void main (String[] args) throws java.lang.Exception
	{	long i,j;
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		Long n=Long.parseLong(br.readLine());
	    long ans=n;
	    for(i=2;i<Math.sqrt(n)+1;i++)
	    {   if(n%i==0)
	        {ans=i;break;}
	    }
	    System.out.println(n/ans);
	}
}