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 nn  {


    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        if(n%2==0){
            System.out.println(n/2);
        }
        else if(n%3==0){
            System.out.println(n/3);
        }
        else if(n%5==0){
            System.out.println(n/5);
        }
        else if(n%7==0){
            System.out.println(n/7);
        }

    }


    }
