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.io.*;
import java.util.*;

public class Towers {
    public static void main(String args[]) {
      Scanner input = new Scanner(System.in);
      long  n = input.nextLong();
      
      long count = 0;
      boolean is_prime = true;
	  
	  int temp = 0;
      for ( int i = 2; i <= Math.sqrt(n); i++){ 
	     if ( n % i == 0 ){
			 temp = i;
			 is_prime = false;
			 break;
	  }
      }
	  
	  if ( is_prime ){
		  count = 1;
	  }
	  else {
	      count =  1 + ( n - (long)temp ) / 2;
	  }
	  
      System.out.println(count);
   }
}
