loop do
  h, w = gets.split(" ").map{|x| x.to_i}
  if h != 0 && w != 0
    (h / 2).times {
      puts (("#" + ".") * w)[0..(w - 1)]
      puts (("." + "#") * w)[0..(w - 1)]
    }
    puts (("#" + ".") * w)[0..(w - 1)] if h % 2 == 1
    puts ""
  else
    break
  end
end