#!/usr/bin/env ruby

if __FILE__ == $0
	loop do
		h, w = gets.split.map { |x| x.to_i }
		if h == 0 and w == 0 then
			break
		end

		h.times do |i|
			w.times do |j|
				print (i+j) % 2 == 0 ? '#' : '.'
			end
			puts
		end
		puts
	end
end

