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.Scanner;

public class Main {
    static long n;
    static int[] arr;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextLong();
        if(n%2==0) System.out.println(n/2);
        else{
            long result = getPrime();
            if(result==-1) System.out.println(1);
            else{
                n -= result;
                result = n/2+1;
                System.out.println(result);
            }
        }
    }

    private static long getPrime(){
        for(long i=3;i*i<=n;i++){
            if(n%i==0) return i;
        }
        return -1;
    }
}