class Main
  def self.run
    chessborads = read_inputs
    puts chessborads.map(&:draw).join("\n")
    puts "\n"
  end

  private

  def self.read_inputs
    chessborads = []
    while true do
      h, w = gets.split(" ").map(&:to_i)
      case [h, w]
        when [0, 0] then break
        else chessborads << Chessboard.new(h, w)
      end
    end
    chessborads
  end
end

class Chessboard
  def initialize(height, width)
    @height, @width = height, width
  end

  def draw
    output = ""
    (1..@height).each {|i|
      line = (i % 2 == 0 ? ".#" : "#.") * (@width / 2 + 1)
      output << "#{line.slice(0, @width)}\n"
    }
    output
  end
end

Main.run