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 input = new Scanner(System.in);
    	long n = input.nextLong();
    	boolean t = true;
    	for(int i = 2 ; i<=Math.sqrt(n) ; i ++) {
    		if(n % i == 0) {
    			if(n % 2 == 0) {
    				System.out.println(n/2);
    			}
    			else {
    				System.out.println(1+(n-i)/2);
    			}
    			t = false;
    			break;
    		}
    		//System.out.println(i);
    	}
    	if(t) {
    		System.out.println(1);
    	}
    }
}