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 Solution {

    public static void main(String[] args) {
        Scanner In = new Scanner(System.in);
        long number = In.nextLong();
        long veces = 0;
        if (number % 2 == 0) {
            veces = (long) number / 2;
        } else {
            long prime = 2;
            while (number % prime != 0) {
                prime++;
            }
            veces = (long) (number / prime);
        }
        System.out.println(veces);
    }
}
