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.*;

public class divisorsubtraction {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long iter = (long)Math.sqrt(n);
		
		if (n % 2 == 0) {
			System.out.println(n/2);
		}
		else {
			boolean found = false;
			for (int i = 3; i <= iter; i+=2) {
				if (n % i == 0) {
					n -= i;
					found = true;
					break;
				}
			}
			if (found) {
				System.out.println(n/2+1);
			}
			else {
				System.out.println(1);
			}
		}

	}


}
