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.
//package Contests.Round54;

import java.util.Scanner;

public class B_SubtractDivisor {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long n = scanner.nextLong();
        long count = 0;
        boolean flag;


        flag = true;
        for (int i = 2; i < Math.sqrt(n) + 1; i++) {
            if (n % i == 0) {
                long k = n / i;
                count += k;
                flag = false;
                break;
            }
        }
        if (flag) {
            count = 1;
        }


        System.out.println(count);
    }
}
