def draw_chessboard(h, w)
  h.times do |i|
    w.times do |j|
      if (i + j).even?
        print "#"
      else
        print "."
      end
    end
    print "\n"
  end
  print "\n"
end

loop do
  h, w = gets.chomp.split(" ").map(&:to_i)
  break if h == 0 && w == 0
  draw_chessboard(h,w)
end