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 Teste {
	
	public static void main(String args[]) {
		
		//Input values
		Scanner input = new Scanner(System.in);
		long n = input.nextLong();
		input.close();
		
		//Logica
        long resp = 0;
        if(n%2==0){
			System.out.println(n/2);
		} else{
 
			for(int i=2;i<=Math.sqrt(n);i++){
				if(n%i==0){
					n-=i;
					resp++;
					break;            
				}
			}
			if(resp == 0){
				resp = 1;
				System.out.println(resp);
				System.exit(0);
			}
			resp += n/2;
			System.out.println(resp);
		}
	}
}
  			  	 			  	 		  					 					