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 Solution2 {
    public static long getMinPrime(long n){
        for(long i = 2; i * i <= n; i++){

            if(n % i == 0){
                return (n - i) / 2 + 1;
            }
        }
        return 1;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        Long n = scanner.nextLong();

        System.out.println(getMinPrime(n));
    }
}

		     	    		 	 	   	 		 					