using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter a positive number: ");

        int num = int.Parse(Console.ReadLine());

        int divider = 2;

        int maxDivider = (int)Math.Sqrt(num);

        bool prime = true;

        while (prime && (divider <= maxDivider)) {

            if (num % divider ==0) {

                prime = false;

            }

            divider++;

        }

        Console.WriteLine("Prime? " + prime);

    }

}