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 q2
{
	public static void main(String ar[])
	{
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long sq = (long)Math.sqrt(n);
		int k = 2;
		boolean flag = false;
		while(k<=sq)
		{
			if(n%k==0)
			{
				flag = true;
				break;
			}
			else
			{
				k++;
			}
		}
//		System.out.println(k);
		if(flag)
		{
			long ans = n/k;
			System.out.println(ans);
		}
		else
		{
			System.out.println(1);
		}
		
	}
}