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 {
	static long isPrime(long n) {
		for (long i = 2; i <= Math.sqrt(n); i++) {
			if (n % i == 0)
				return i;
		}
		return -1;
	}

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int t = 100;
		long n = sc.nextLong(), isP = isPrime(n);
		if (isP == -1)
			System.out.println(1);
		else {
			System.out.println((n - isP) / 2);
		}
	}
}
