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 DivisorSubtraction {


    public static void main(String[] args) {

        Scanner s=new Scanner(System.in);
        long N=s.nextLong(),f=0;

        for(long i=2;i*i<=N;i++){
            if(N%i==0){
                f=i;
                break;
            }
        }

        if(f==0){
            System.out.println(1);
            return;
        }

        if(N%2==0){
            System.out.println(N/2);
            return;
        }

        N=N-f;

        System.out.println(1+ (N/2));


    }
}
