while true
	h,w = gets.split.map(&:to_i)
	break if h == 0 && w == 0
	for i in (1..h) do
		for j in (1..w) do
			if (i+j)% 2 == 0
				print "#"
			else
				print "."
			end
		end
		puts
	end
	puts
end
