loop do
	h, w = gets.split.map(&:to_i)
	if h == 0 && w == 0 then
		break
	end
	
	h.times do |i|
		w.times do |j|
			if (i + j) % 2 == 0 then
				print("#")
			else
				print(".")
			end
		end
		puts
	end
	puts
end

