A book has 299 pages, how many digital page numbers are needed?
一本书共299页，需多少个数码编页码？
<gadget id="calculator">2 * 90</gadget>
<output>180</output>

<gadget id="calculator">3 * 200</gadget>
<output>600</output>

<gadget id="calculator">9 + 180 + 600</gadget>
<output>789</output>

<result>789</result>