using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ITP1_5
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                string[] strArray = Console.ReadLine().Split(' ');
                int height = int.Parse(strArray[0]);
                int width = int.Parse(strArray[1]);

                if (height == 0 && width == 0)
                {
                    break;
                }

                string line0 = "";
                string line1 = "";
                bool even = true;
                for (int i = 0; i < width; ++i)
                {
                    if (even)
                    {
                        line0 += '#';
                        line1 += '.';
                    }
                    else
                    {
                        line0 += '.';
                        line1 += '#';
                    }
                    even = !even;
                }

                even = true;
                for (int i = 0; i < width; ++i)
                {
                    if (even)
                    {
                        Console.WriteLine(line0);
                    }
                    else
                    {
                        Console.WriteLine(line1);
                    }
                    even = !even;
                }
                Console.WriteLine();

            }
        }
    }
}