using System;
using System.Linq;

namespace AOJ_Practice
{
    class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                var inputs = Console.ReadLine().Split(' ').Select(int.Parse).ToList();
                if (inputs.All(x => x == 0))
                {
                    goto Finish;
                }

                var height = inputs[0];
                var width = inputs[1];

                for (int i = 0; i < height; i++)
                {
                    var firstChar = i % 2 == 0 ? '#' : '.';
                    var secondChar = i % 2 == 0 ? '.' : '#';
                    for (int j = 0; j < width; j++)
                    {
                        Console.Write(j == 0 ? firstChar : secondChar);
                    }
                }

                Console.WriteLine();
            }

            Finish:
            return;
        }
    }
}

