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 Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long n = scanner.nextLong();
        long count=0;
        for(long i=3;i<=n;i+=2){
            if (n%2==0){
                n=n-i;
                count++;
                i=2;
            }else if (IsPrime(i)&&n%i==0){
                n=n-i;
                count++;
                i=2;
            }
            if (n==0){
                break;
            }
        }
        System.out.println(count);
    }

    public static boolean IsPrime(long n){
        int i=0;
        for (i=2;i<=Math.sqrt(n);i++){
            if (n%i==0){
                return false;
            }
        }
        return true;
    }
}

