namespace ITP1_5_C
{
    class Program
    {
        static void Main(string[] args)
        {
            var list = new List<int[]>();
            string input;
            while ((input = Console.ReadLine()) != "0 0")
                list.Add(input.Split(' ').Select(x => Convert.ToInt32(x)).ToArray());
            foreach (var l in list)
            {
                for (int height = 0; height < l[0]; height++)
                {
                    bool patis;
                    if (height % 2 == 0) patis = true;
                    else patis = false;
                    for(int width = 0; width < l[1]; width++)
                    {
                        if (patis) Console.Write("#");
                        else Console.Write(".");
                        patis = !patis;
                    }
                    Console.WriteLine();
                }                   
                Console.WriteLine();
            }
        }
    }
}