loop do
	h, w = gets.chomp.split.map(&:to_i)
	break if h == 0 && w == 0
	h.times do |i|
		if i%2 == 0
			puts (w%2 == 0 ? "#."*(w/2) : "#."*(w/2) << "#")
		else
			puts (w%2 == 0 ? ".#"*(w/2) : ".#"*(w/2) << ".")
		end
	end
	puts
end