loop do
  h,w = gets.split.map(&:to_i)
  break if h==0&&w==0
  width = 0
  height = 0
  h.times do
    w.times do
      if (height + width)%2 == 0
        print "#"
      else
        print "."
      end
      width += 1
    end
    width = 0
    height += 1
    puts
  end
  puts
end
