loop do
  h,w = gets.split.map(&:to_i)
  break if h == 0 && w == 0

  1.upto(h) do |v|
    if v.odd?
      1.upto(w) do |wv|
        if wv.odd?
          print '#'
        else
          print '.'
        end
      end
    else
      1.upto(w) do |wv|
        if wv.odd?
          print '.'
        else
          print '#'
        end
      end
    end
    puts
  end
  puts
end