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 Prime {
    public static  void main(String args[]){
        Scanner in = new Scanner(System.in);
      System.out.println(Check(in.nextDouble(),0));
    }

    private static int Check(double number, int i) {

        if(IsPrime(i)){
            if(number%i==0){
                return (int) (number / i);
            }

        }
        return Check(number,i+1);
    }

    private static boolean IsPrime(int no) {
        for(int i = 1;i<no;i++ ){
            if(no%i==0){
                return  true;
            }
        }
        return false;
    }
}
