using System;

public class Program

{

    public  static void Main(string[] args)

        {

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

            int length = Int32.Parse(Console.ReadLine());

​

            int[,] arr = new int[length, length];

            int numConcentricSquares = (int)Math.Ceiling((length) / 2.0);

            int sideLen = length;

            int currNum = 0;

​

            for (int i = 0; i < numConcentricSquares; i++)

            {

​

                for (int j = 0; j < sideLen; j++) arr[i + j, i] = ++currNum;

​

                for (int j = 1; j < sideLen - 1; j++) arr[length - 1 - i, i + j] = ++currNum;

​

                for (int j = sideLen - 1; j > 0; j--) arr[i + j, length - 1 - i] = ++currNum;

​

                for (int j = sideLen - 1; j > 0; j--) arr[i, i + j] = ++currNum;

​

                sideLen -= 2;

            }

​

​

            for (int i = 0; i < arr.GetLength(0); i++)

            {

                for (int j = 0; j < arr.GetLength(1); j++) Console.Write("{0, 4}", arr[i, j]);

                Console.WriteLine();

            }

        }

    }

​