using System;

public class Program

{

        public static void Main()

        {

            int n;

            Console.Write("Input: ");

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

            print_square(n);

            Console.ReadLine();

        } 

​

        static void print_square(int n)

        {

            int i, j;

​

            for (i = 1; i <= n; i++)

            {

                for (j = 1; j <= n; j++)

                {

                    if (i == 1 || i == n ||

                        j == 1 || j == n)

                        Console.Write("*");

                    else

                        Console.Write(" ");

                }

                Console.WriteLine();

            }

​

        }

}