loop do
	h, w = gets.split.map(&:to_i)

	break if (h == 0 && w == 0)

	h.times do |y|
		if y % 2 == 0 then
			i = 1
		else
			i = 2
		end

		w.times do
			if i % 2 == 0 then
				print '.'
			else
				print '#'
			end

			i += 1
		end

		print "\n" 
	end

	print "\n"
end