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 verylong {

	public static void main(String[] args) {
		Scanner msc = new Scanner(System.in);
		long number = msc.nextLong();
		number -= getPrimeFacts(number).get(0);
		System.out.println(1 + number/2);
	}
	static ArrayList<Long> getPrimeFacts(long input){
		ArrayList<Long> list = new ArrayList<Long>();
		for(long i = 2 ; i * i <= input; i++){
			while(input % i == 0){
				input /= i;
				list.add(i);
			}
		}
		if(input != 1){
			list.add(input);
		}
		return list;
	}
}
