def draw_check_line(h, w, i)
	pattern = ['#', '.']
	if i%2 == 1
		p_index = 0
	else
		p_index = 1
	end

	w.times do
		print("#{pattern[p_index%2]}")
		p_index += 1
	end
	puts ""
end
def draw_check(h, w)
	for i in 1..h
		draw_check_line(h, w, i)
	end
	puts ""
end

inputs = gets.strip().split(" ")
h  = inputs[0].to_i
w  = inputs[1].to_i
until h == 0 && w == 0
	draw_check(h, w)
	inputs = gets.strip().split(" ")
	h  = inputs[0].to_i
	w  = inputs[1].to_i		
end
