using System;

class Rectangle
{
    public static void Main()
    {
        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;
            }

            for (int i = 0; i < H; i++) {
                for (int j = 0; j < W; j++){
                    if (i % 2 == 0)
                    {
                        for (int k = 0; k < W / 2; i += 2)
                        {
                            Console.Write("#.");
                        }
                        if (j % 2 == 1)
                        {
                            Console.Write("#");
                        }
                    }
                    else
                    {
                        for (int k = 0; k < W / 2; i += 2)
                        {
                            Console.Write(".#");
                        }
                        if (j % 2 == 1)
                        {
                            Console.Write(".");
                        }
                    }
                    Console.WriteLine();
                }
            }
            Console.WriteLine();
        }
    }
}
