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.
/*
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 * and open the template in the editor.
 */


import java.util.Scanner;

/**
 *
 * @author Vessi
 */
public class Test {

    void run() {
        Scanner in = new Scanner(System.in);

        long n = in.nextLong();

        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (n % i == 0 && isPrime(i)) {
                if (i == 2) {
                    System.out.println(n / i);
                    return;
                }
                System.out.println( (n - i) / 2 + 1);
                return;
            }
        }

        System.out.println(1);
    }

    boolean isPrime(int n) {
        if (n == 2) {
            return true;
        }
        //check if n is a multiple of 2
        if (n % 2 == 0) {
            return false;
        }
        //if not, then just check the odds
        for (int i = 3; i * i <= n; i += 2) {
            if (n % i == 0) {
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        new Test().run();
    }
}
