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.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Scanner;

public class Main {

    static boolean[] p;

    public static long getTheNumber(long n) {
        int interesting = (int)(Math.sqrt(n));

        p = new boolean[interesting + 1];
        int i, j;
        for (i = 2; i <= interesting; ++i) {
            if (!p[i]) {
                if (n % i == 0) {
                    return i;
                }
                for (j = i + i; j <= interesting; j += i) {
                    p[j] = true;
                }
            }
        }
        return n;
    }

    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);

        long n = s.nextLong();

        long smallestPrime = getTheNumber(n);
        System.out.println(n / smallestPrime);

    }
}
