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 Divisor_Subtraction
{
    public static void main(String args[])
    {
        Scanner s1 = new Scanner(System.in);
        long n = s1.nextLong();
        if(n % 2 == 0)
            System.out.println(n/2);
        else
            if(isprime(n))
                System.out.println("1");
            else
                for(int i=2;i<=(int)Math.sqrt(n);i++)
                    if(n % i == 0)
                    {
                        System.out.println(1+(n-i)/2);
                        break;
                    }
    }
    public static boolean isprime(long n)
    {
        for(int i=2;i<=(int)Math.sqrt(n);i++)
            if(n % i == 0)
                return false;
        return true;
    }
}