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 class182 {
	public static long prime(long x)
	{
		int flag=0;
		for(long i=2;i*i<=x;i++)
		{
			if(x%i==0)
			{
				flag=1;
				return 0;
			}
		}
		return 1;
	}
public static void main(String arg[])
{
	
	Scanner sc=new Scanner(System.in);
	long n=sc.nextLong();
	long flag=prime(n);
	if(flag==1)
	{
		System.out.println(1);
	}
	else
	{
		long i=2;
		long c=0;
		while(n>0)
			{
			flag=prime(i);
			if(flag==0)
			{
				i++;
			}
			else
			{
				if(n%i==0)
				{
				if(n%2==1)
				{
					n=n-i;
					i=2;
					c++;
				}
				else
				{
					c+=n/i;
					break;
				}
				}
				else
				{
					i++;
				}
				
			}
			}
			
		
		System.out.println(c);
	}
	
	
	
}
}
