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 B {

	public static void main(String[] args) {
		
		Scanner s = new Scanner(System.in);
		long l = s.nextLong();
		if (l == 0) {
			System.out.println("0");
			return;
		}
		long smallest = -1;
		for (int i = 2; i < Math.sqrt(l) + 1; i++) {
			if (l % i == 0) {
				smallest = i;
				break;
			}
		}
		if (smallest == -1) {
			smallest = l;
		}
		System.out.println(l / smallest);
		
	}
	
}
