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 B1076 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        long a=sc.nextLong();
        long aa=0;
        for (long i=2;i<=Math.sqrt(a);i++)
        {
            if (a%i==0)
            {
                aa=i;break;
            }
        }
        if (aa==0)
        {System.out.println("1");

        }else {
            System.out.println((a-aa)/2+1);
        }
    }
}
