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 testing{

	public static void main(String[] args) throws Exception {
	
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		
		
		if(n % 2 == 0) System.out.println(n / 2);
		else {
			for(long i = 3; i * i <= n ; i += 2) {
				//System.err.println(i);
				if(n % i == 0) {
					System.out.println(1 + (n - i) / 2);
					return;
				}
			}
			System.out.println(1);
		}
		
	}
	

	
	
	
	
}