using System;

public class Program

{

    public static void Main()

    {

        int size = 0;

        Console.Write("Enter square size: ");

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

        if (size > 20)

            size = 20;

        for (int i = 1; i <= size; i++)

        {

            for (int j = 1; j <= size; j++)

            {

                if ((i == 1 || i == size || j == 1 || j == size))

                    Console.Write("* ");

                else

                    Console.Write("  ");

            }

          Console.WriteLine();

        }

    }

}