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.
//package Codef;

import java.util.Scanner;

public class B_1076 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		// System.out.println(prime(10));
		long n = s.nextLong();
		long c = 1;
		for (int i = 2; i <= Math.sqrt(n); i++) {
          if(n % i ==  0) {
        	  c+=(n-i)/2;
          }
		}
		System.out.println(c);
	}
}
