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 Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		Scanner sc=new Scanner (System.in);
		long n=sc.nextLong();
		System.out.println(algo(n));
	}
	static long algo(long n)
	{
		if((n&1)==0)
		return n/2;
		else
		{
		long i=0,c=0;
		for(i=3;i<=Math.sqrt(n);i+=2)
		if(n%i==0)
		{
			c=1;
			break;
		}
		if(c==1)
		return 1+(n-i)/2;
		else
		return 1;
		}
		
	}
}