#3PrimeNumberCheck

static void Main()
        {
            //first version
            Console.Write("Enter a number: ");
            sbyte number = sbyte.Parse(Console.ReadLine());
            bool isPrime = ((number % 2 != 0) && (number % 3 != 0) && (number % 5 != 0) && (number % 7 != 0) && (number != 1));
            bool primeCases = ((number == 2) || (number == 3) || (number == 5) || (number == 7));
            Console.WriteLine((isPrime || primeCases) ? "{0} is prime." : "{0} is not prime.", number);

            //second version
            //Console.WriteLine("Enter a random number to check if it's prime:");
            //int number = int.Parse(Console.ReadLine());
            //double numberSqrt = Math.Sqrt(number);
            //int numberSqrtRound = (int)Math.Round(numberSqrt);
            //if (number == 0 || number == 1)
            //{
            //    Console.WriteLine(number + " is not a prime number");
            //}
            //else
            //{
            //    for (int i = 2; i <= numberSqrtRound; i++)
            //    {
            //        if (number % i == 0)
            //        {
            //            Console.WriteLine(number + " is not a prime number.");
            //            return;
            //        }
            //    }
            //    Console.WriteLine(number + " is a prime number.");
            //}
        }