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.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author ky112233
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        BDivisorSubtraction solver = new BDivisorSubtraction();
        solver.solve(1, in, out);
        out.close();
    }

    static class BDivisorSubtraction {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            long n = in.nextLong();
            if (n % 2 == 0) {
                out.println(n / 2);
            } else {
                boolean flag = true;
                for (long i = 2; i * i <= n; i++) {
                    if (n % i == 0) {
                        flag = false;
                        n -= i;
                        break;
                    }
                }
                if (flag) {
                    out.println(1);
                } else {
                    out.println(1 + n / 2);
                }
            }
        }

    }
}

