The page number of a book consists of 7641 digits. How many pages does this book have?
一本书的页码由7641个数码组成，这本书共有多少页？
<gadget id="calculator">2 * 90</gadget>
<output>180</output>

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

<gadget id="calculator">7_641 - 9 - 180 - 2_700</gadget>
<output>4_752</output>

<gadget id="calculator">4_752 / 4</gadget>
<output>1_188</output>

<gadget id="calculator">1_188 + 900 + 90 + 9</gadget>
<output>2_187</output>

<result>2_187</result>