while ((h,w = gets.split(" ").map(&:to_i)).select{|i| i != 0}.length > 0) do
  h.times do |i|
    w.times do |j|
      print (i%2==0) ? ((j%2==0) ? "#" : ".") : ((j%2==0) ? "." : "#")
      puts "" if (j == w-1)
    end
  end
  puts ""
end