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;
import java.util.HashMap;
import java.util.Arrays;
public class Codechef{
 

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