loop do
	nums = gets.chomp.split(" ").map(&:to_i)
	break if nums == [0,0]
	for h in (0...nums[0]) do
		for w in (0...nums[1]) do
			if (h.odd? && w.odd?) || (h.even? && w.even?)
				print "#"
			elsif 
				print "."
			end
		end
		puts
	end
	puts
end