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 Main {

	public static void main(String[] args) {		
	
		Scanner scan = new Scanner(System.in);	
	
		long n = scan.nextLong();		

		boolean isPrime = true;
		long prime = - 1;
		for (long i = 2;i * i <= n;i ++) {
			if (n % i == 0) {
				isPrime = false;
				prime = i;
				break;
			}
		}
		if (isPrime) {
			System.out.println(1);
		} else {			
			if (n % 2 == 0) {
				System.out.println(n / 2);
			} else {
				System.out.println(1 + (n - prime) / 2);				
			}			
		}
		
	}
	
	
	
}













