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 Solution {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		
		long input = Long.parseLong(scanner.nextLine());
		
		long count = 0;
		
		while(input > 0) {
			
			if(input % 2 == 0) {
				count = input / 2;
				break;
			} else {
				long divisor = getNextDivisor(input);
				input = input - divisor;
				count++;
				
			} 
			
			
			
			
		}
		
		System.out.println(count);
		
		
		 
		
		
		

	}

	private static long getNextDivisor(long input) {
		for(long i = 3; i < Math.sqrt(input); i = i + 2) {
			if(input % i == 0) {
				return i;
			}
		}
		return input;
	}

}
