using System;


namespace ConsoleApplication13
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true) {
                String[] s = Console.ReadLine().Split(' ');
                int H = int.Parse(s[0]);
                int W = int.Parse(s[1]);

                if (H == 0 && W == 0) break;
            
                int i = 0;
                while (true)
                {
                    if (i == H) break;
                    if (i%2==0)
                    {
                        for (int x = 0; x < W; x++)
                        {
                            Console.Write("#.");

                        }
                    }
                    else
                    {
                        for (int x = 0; x < W; x++)
                        {
                            Console.Write(".#");

                        }
                    }
                    
                    Console.WriteLine();

                    i++;
                }
                Console.WriteLine();


            }

        }
    }
}