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 Main{ 
static long divisor(long n)  
{  
    if (n % 2 == 0) return n/2;  
    for (long i = 3; i<=Math.sqrt(n); i++)  if (n % i == 0) return ((n-i)/2)+1;  
    return 1;  
}  
    public static void main (String[] args) { 
      
        Scanner sc=new Scanner(System.in);
        long n = sc.nextLong(); 
        System.out.println (divisor(n));  
          
    } 
} 