It takes 6869 numbers to number the pages of an encyclopedia, so how many pages does this book have?
给一部百科全书编上页码需要6869个数字，那么这部书共有多少页．
<gadget id="calculator">90 * 2</gadget>
<output>180</output>

<gadget id="calculator">900 * 3</gadget>
<output>2_700</output>

<gadget id="calculator">6_869 - 9 - 180 - 2_700</gadget>
<output>3_980</output>

<gadget id="calculator">3_980 / 4</gadget>
<output>995</output>

<gadget id="calculator">995 - 1</gadget>
<output>994</output>

<gadget id="calculator">1_000 + 994</gadget>
<output>1_994</output>

<result>1_994</result>