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