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 DivisorSubtraction {

    public static long isPrime(long n) {
        for (long i = 2; i * i <= n; ++i) {
            if (n % i == 0) {
                return i;
            }
        }
        return n;
    }

    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        long n = scan.nextLong();
        if (n % 2 == 0) {
            System.out.println(n / 2);
        } else {
            System.out.println(((n - isPrime(n)) / 2) + 1);
        }

    }
}
