while line = gets do
  h, w = line.split.map(&:to_i)
  if h == 0 && w == 0 then break end
  h.times do |i|
    w.times do |j|
      if (i + 1) % 2 == 0 || (j + 1) % 2 == 0
        print "."
      else
        print "#"
      end
    end
    puts
  end
  puts
end