using System;

// Kiem tra mot so co phai la so nguyen to khong ?

namespace ConsoleApp42

{

    class Program

    {

        static void Main(string[] args)

        {

            // Kiem tra 1 so co phai la so nguyen to khong ?

​

            int n;

​

            Console.Write("Nhap so n can kiem tra n = ");

​

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

​

            if (n == 0 || n == 1)

​

            {

                Console.WriteLine($"{n} khong phai la so nguyen to");

​

                Console.ReadLine();

            }

​

            else

​

            {

                for (int i = 2; i <= n / 2; i++)

​

                {

                    if (n % i == 0)

​

                    {

​

                        Console.WriteLine($"{n} khong phai la so nguyen to");

​

                        return;

                    }

​

                    else

​

                    {

                        Console.WriteLine($"{n} la so nguyen to");

                    }

​

                    Console.ReadLine();

​

                } 

​

            }

        }

    }

}