using System;

public class Program

{

    public static void Main()

    {

        Console.Write("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);

​

    }

}