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.net.Inet4Address;
import java.util.*;
import java.io.*;

public class No_I_Did_Not {

    public static boolean is_prime(int n)
    {
        for(int i = 2 ; i <= Math.sqrt(n) ; i++)
        {
            if(n % i == 0)
                return false;
        }
        return true;
    }


    public static void main(String[] args)throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);

        Long n = Long.parseLong(br.readLine());
        long res = 1l;
        long min = 0;

        for(int i = 2 ; i <= Math.sqrt(n) ; i++)
        {
            if(is_prime(i))
            {
                if(n % i == 0)
                {
                    min = i;
                    res *= (1l*n)/(1l*i);
                    break;
                }
            }
        }

        if(min == 0)
            out.println(1);
        else
            out.println(res);




        out.flush();
        out.close();

    }

}
