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.io.PrintWriter;
import java.util.*;

public class Test {

    static long mind(long n){
        for(int i = 2; i*i<=n; i++){
            if(n%i==0) return i;
        }
        return n;
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long n = in.nextLong(), d = mind(n);
        System.out.println(d==n?1:((n-d)/2+2));
    }

}