The page number of a novel must use 1989 numbers when printing. How many pages does this book have?
一本小说的页码，在印刷时必须用1989个数字，这本书共有多少页．
<gadget id="calculator">2 * 90</gadget>
<output>180</output>

<gadget id="calculator">1_989 - 9 - 180</gadget>
<output>1_800</output>

<gadget id="calculator">1_800 / 3</gadget>
<output>600</output>

<gadget id="calculator">9 + 90 + 600</gadget>
<output>699</output>

<result>699</result>