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.*;
import java.util.*;
public class Main{
    public static void main(String[] args) throws IOException{
        PrintWriter pr=new PrintWriter(System.out);
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        Scanner scan=new Scanner(System.in);
        long n=scan.nextLong();
        int sub=0;
            long i=2;
            for(;i*i<=n;i++)
                if(n%i==0){
                    long ans=n/i;
                    System.out.print(ans);
                    break;
                }
            if(i*i>n){
                System.out.print("1");}



    }

}