book, Xiao Ming read from page 2 to page 5, how many pages did he read?
一本书，小明从第2页看到第5页，他看了多少页．
<gadget id="calculator">5 - 2</gadget>
<output>3</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>