Xiaohong reads a story book. She reads half of the book on the first day, 15 pages on the second day, and 13 pages on the third day. How many pages are there in this book?
小红看一本故事书，第一天看了全书的一半，第二天看了15页，第三天看了13页，正好看完．这本书一共多少页？
<gadget id="calculator">15 + 13</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>