Xiao Pang bought a story book with 72 pages in total. How many numbers are used to compile the page numbers of this book?
小胖买了一本故事书，一共有72页，编这本书的页码一共用了多少个数字．
<gadget id="calculator">9 * 1</gadget>
<output>9</output>

<gadget id="calculator">63 * 2</gadget>
<output>126</output>

<gadget id="calculator">9 + 126</gadget>
<output>135</output>

<result>135</result>