Dongdong read a story book, read 12 pages on the first day, and 18 pages on the second day. How many pages should he read on the third day.
冬冬看一本故事书，第一天看了12页，第二天看了18页．第三天他应该从第多少页看起．
<gadget id="calculator">12 + 18 + 1</gadget>
<output>31</output>

<result>31</result>