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 helloWorld 
{
	public static void main(String[] args) 
	{		
		Scanner in = new Scanner(System.in);
		long n = in.nextLong();
		long d = 2, ans = 1;
		boolean p = true;
		
		for(; d * d <= n; d++)
			if(n % d == 0) {
				p = false;
				break;
			}
		
		if(n % 2 == 0)
			ans = n/2;
		else
			if(!p)
				ans += (n-d) / 2;
		
		System.out.println(ans);
		
		in.close();
	}
}
