while true do
   h, w = gets.split.map(&:to_i)
   if h == 0 && w == 0
      break
   end
   h.times do |i|
      if i % 2 == 0
         outputs = []
         w.times do |h|
            if h % 2 == 0
               outputs << "#"
            else
               outputs << "."
            end
         end
         outputs.each do |output|
            print output
         end
         print "\n"
      else
         outputs = []
         w.times do |h|
            if h % 2 == 0
               outputs << "."
            else
               outputs << "#"
            end
         end
         outputs.each do |output|
            print output
         end
         print "\n"
      end
   end
   puts ""
end