It takes 789 numbers to number the pages of a book. How many pages does this book have?
给一本书编上页码共要用789个数字，这本书有多少页？
<gadget id="calculator">90 * 2</gadget>
<output>180</output>

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

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

<gadget id="calculator">99 + 200</gadget>
<output>299</output>

<result>299</result>