A book with 50 pages, read 20 pages on the first day and 15 pages on the second day, what page should be read from the third day.
一本书50页，第一天读了20页，第二天读了15页，第三天应从第多少页读起．
<gadget id="calculator">20 + 15 + 1</gadget>
<output>36</output>

<result>36</result>