input = gets.chomp.split("\s")
h, w = input[0].to_i, input[1].to_i

def output(h, w)
	arr = []
	for i in 1..w
		if h % 2 == 0
			if i % 2 == 0
				arr = arr + ["#"]
				out = arr.join
			else
				arr = arr + ["."]
				out = arr.join
			end
		else
			if i % 2 == 0
				arr = arr + ["."]
				out = arr.join
			else
				arr = arr + ["#"]
				out = arr.join
			end
		end
	end
	
return out
end

until (h == 0) && (w == 0)
	for i in 1..h
		out = output(i, w)
	puts out
	end
	
puts ""
input = gets.chomp.split("\s")
h, w = input[0].to_i, input[1].to_i
end