loop do
  h, w = gets.chomp.split.map(&:to_i)
  break if h == 0 && w == 0
  for j in 0..(h - 1) do
    s = ""
    for i in 0..(w - 1) do
      s += i.odd? && j.odd?  || i.even? && j.even? ? "#" : "."
    end
    puts s
  end
  puts "\n"
end
