while true
	h,w = gets.chomp.split(" ").map(&:to_i)
	break if h == 0 && w == 0
	h.times do |i|
		w.times do |j|
			if (i + 1) % 2 == 0
				if (j + 1) % 2 == 0
					print "#"
				else
					print "."
				end
			elsif
				if (j + 1) % 2 == 0
					print "."
				else
					print "#"
				end
			end
		end
		print "\n"
	end
	print "\n"
end