import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc = new Scanner(System.in);

		while (true)
		{
			int h = sc.nextInt();
			int w = sc.nextInt();

			if (h == 0 && w == 0)
			{
				break;
			}

			for (int i = 0; i < h; i++)
			{
				for (int j = 0; j < w; j++)
				{
					if ((i + j) % 2 == 0)
					{
						System.out.print("#");
					}
					else
					{
						System.out.print(".");
					}
				}
				System.out.println();
			}

			System.out.println();
		}
	}
}

