using System;

namespace PrintCheckboard
{
	class MainClass
	{
		public static void Main (string[] args)
		{
			while (true) {
				string[] tmp = Console.ReadLine ().Split (" ".ToCharArray ());
				int height, Wide;

				height = int.Parse (tmp [0]);
				Wide = int.Parse (tmp [1]);
				if (height == 0 && Wide == 0)
					break;

				for (int i = 0; i < height; i++) {
					for (int j = 0; j < Wide; j++) {
						Console.Write (((i*height+j)%2 == 0)? "#":".");
					}
					Console.Write ("\n");
				}
				Console.Write ("\n");
			}
		}
	}
}