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.nextInt();
        long n1 = n;
        long subs = 0 ;
        if (n % 2 != 0 && n % 3 != 0 && n % 5 != 0 && n % 7 != 0){
            System.out.println(0);
        }
        else if (n == 2 || n == 3 || n == 5 || n == 7){
            System.out.println(0);
        }
       else if(n==0||n==1){
            System.out.println(0);
        }
        else {
            while (n1 >= 2) {
                n = n1;
                for (;;) {
                    if (n%7==0&&n!=7) {
                        n = n/7;
                    }
                    else if (n%5==0&&n!=5){
                        n =n / 5;
                    }
                    else if (n%3==0&&n!=3){
                        n = n/3;
                    }
                    else if (n%2==0&&n!=2){
                        n =n/2;
                    }
                else {
                        if (n1 % n == 0) {
                            break;
                        }
                    }

                }
                n1 = n1 - n;
                
                subs++;
            }


            System.out.println(subs);
        }
    }


    }
