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.*;
import java.io.*;
public class DivisorSubtraction
{
	public static void main(String[] v)
	{
		long n;
		Scanner sc=new Scanner(System.in);
		n=sc.nextLong();
		long m=myfirstprimefactor(n);
		System.out.println((n/m));
	}
	static long myfirstprimefactor(long n)
	{
		long l=2;
		if(n%2==0)
			return 2;
		for(l=3;l<=(long)(Math.sqrt(n));l++)
		{
			if(n%l==0)
				return l;
		}
			return n;
	}
}