using System.Linq;
public partial class IntroductionToProgramming{
	public static void Main(){
		string[] line = System.Console.ReadLine().Split(' ');

		int h = int.Parse(line[0]);
		int w = int.Parse(line[1]);

		while (!(h == 0 && w == 0))
		{
			string es = string.Concat(Enumerable.Repeat("#.", w / 2).ToArray()).Substring(0, w);;
			string os = string.Concat(Enumerable.Repeat(".#", w / 2).ToArray()).Substring(0, w);;
			for (int i = 0; i < h; i++ )
			{
				if (i % 2 == 0)
				{
					System.Console.WriteLine(es);
				}
				else
				{
					System.Console.WriteLine(os);
				}
			}
			System.Console.WriteLine(string.Empty);

			string[] line2 = System.Console.ReadLine().Split(' ');

			h = int.Parse(line2[0]);
			w = int.Parse(line2[1]);
		}
	}
}