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;

/**
 * http://codeforces.com/contest/1076/problem/B
 **/
public class TaxiDriversAndLyftSolution {

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

        if (n % 2 ==0) {
            System.out.println(n/2);
        } else {
            for (int i = 3 ; i <= Math.sqrt(n) ; i++) {
                if (n % i == 0) {
                    System.out.println((n-i)/2+1);
                    return;
                }
            }
        }
        System.out.println(1);
    }
}
