using System;

public class Program

{

    private static void WriteBoard(int size)

    {

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

        {   

            if (j%2==0)

                {

                Console.Write(".");

                    for (int i = 2; i<=size; i++)

                    {

                    if (i%2==0)

                        Console.Write("#");

                    else Console.Write(".");

                    }

                }

            else

                {

                    Console.Write("#");

                    for (int i = 2; i<=size; i++)

                    {

                    if (i%2==0)

                        Console.Write(".");

                    else Console.Write("#");                

                    }

                }

            Console.WriteLine();

        }       

    }

​

    public static void Main()

    {

    WriteBoard(7);  

    }

​

}