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.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Scanner;
import java.util.Set;

public class Main {
 static ArrayList <String>list=new ArrayList();static int l=0; static int y=1;
 static String s=""; static String ans ="";
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);boolean flag=false;
		long n=sc.nextLong();long index=0; 
		long i=2;long count=0;
		
  System.out.print(solve(n));
	}
	public static  long solve(long X) {
		for(long  i = 2;i * i <= X;i++) if(X%i == 0) {
			if(i == 2) return X/2;
			return 1 + (X-i)/2;
		}
		return 1;
	}
}	

	


