SquareInsideEmptywithStars

using System;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {

            int n = int.Parse(Console.ReadLine());
            Console.Write(new string('*',n));

            for (int i = 0; i < n-2; i++)
            {
                Console.Write("*");
                Console.Write(new string(' ',n-2));
                Console.WriteLine("*");
            }

            Console.WriteLine(new string('*', n));

        }
    }
}