loop do
	h,w=gets.chomp.split.map(&:to_i)
	break if h==0 && w==0

	h.times do |i|
		w.times do |j|
			if((i.even? && j.even?)||(i.odd? && j.odd?))
				print "#"
			elsif((i.even? && j.odd?)  || (i.odd? && j.even?))
				print "."
			end
		end
		puts
	end
	puts
end