A book has 900 pages. Xiao Ming reads 308 pages in the first week and 281 pages in the second week. How many pages does Xiao Ming not read?
一本书900页，小明第一个星期看了308页，第二个星期看了281页，小明还有多少页没有看？
<gadget id="calculator">900 - 308 - 281</gadget>
<output>311</output>

<result>311</result>