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.Scanner;

public class EduRound54DivsubB {

	public static void main(String[] args) {
	Scanner s = new Scanner(System.in);
	long n = s.nextLong();
	if(n%2==0) {
		System.out.println(n/2);
	}else {
		long count = n;
		for(long i=3;i*i<=n;i+=2) {
			if(n%i==0) {
				count = i; 
				break;
			}
		}
		System.out.println((n-count)/2+1);
	}
	}

}
