h, w = gets.split.map(&:to_i)

while h != 0 || w != 0 do

	for i in 1..h 

		for j in 1..w

			print (i+j)%2 == 0 ? "#" : "." 
			#???????????????

		end

		puts

	end

	h, w = gets.split.map(&:to_i)

end