while (n = gets.split.map(&:to_i)) != [0, 0]
  h, w = n

  h.times do |j|
    w.times do |i|
      if j.odd?
        printf(".") if i.even?
        printf("#") if i.odd?
      else
        printf("#") if i.even?
        printf(".") if i.odd?
      end
    end
    puts
  end
  puts
end