using System;

public class Program

{

    public static bool IsPrimeNumber(int n) {

        bool isPrimeNum = true;

​

        if (n != 2 && (n == 1 || n % 2 == 0)) {

             isPrimeNum = false;

        } else {

            for (int i = 3; i <= n/2; i += 2) {

                    if (n % i == 0) {

                        isPrimeNum = false;

                        break;

                    }

            }

        }

​

        return isPrimeNum;

    }

    public static void Main()

    {

        int[,] nums = {{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, {11, 12, 13, 14, 15, 16, 17, 18, 19, 20}, {21, 22, 23, 24, 25, 26, 27, 28, 29, 30}};

​

        foreach (int i in nums) {

            if (IsPrimeNumber(i))

                Console.Write("{0:D2} ", i);

            else

                Console.Write(" X ");

            if (i % 10 == 0)

                Console.WriteLine();

        }

    }

}