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.math.BigInteger;
import java.util.Scanner;

/**
 * @Created by sbhowmik on 29/12/18
 */
public class DivisorSubtraction {

    static boolean isPrime(long n) {
        // Corner cases 
        if (n <= 1)
            return false;
        if (n <= 3)
            return true;

        // This is checked so that we can skip 
        // middle five numbers in below loop 
        if (n % 2 == 0 || n % 3 == 0)
            return false;

        for (int i = 5; i * i <= n; i = i + 6)
            if (n % i == 0 || n % (i + 2) == 0)
                return false;

        return true;
    }
    public static void main(String []args) {

        Scanner scanner = new Scanner(System.in);
        long n = scanner.nextLong();
        if (n%2 == 0) {
            System.out.print(n/2);
        } else {
            if(isPrime(n)) {
                System.out.print(1);
            } else {
                System.out.print(1 + (n - 3) / 2);
            }
        }
    }
}
