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