How many digits are needed to print the page numbers of a 150-page book?
排印一本150页的书的页码，共需要多少个数码？
<gadget id="calculator">2 * 90</gadget>
<output>180</output>

<gadget id="calculator">3 * 51</gadget>
<output>153</output>

<gadget id="calculator">9 + 180 + 153</gadget>
<output>342</output>

<result>342</result>