All the students in class 4 and 1 stand in a row. When counting from left to right, Xiaohua newspaper: 18; when counting from right to left, Xiaohua newspaper: 13. So, how many students are there in this class?
四1班全体同学站成一排，当从左往右报数时，小华报：18；当从右往左报数时，小华报：13．那么，该班有学生多少名．
<gadget id="calculator">17 + 12 + 1</gadget>
<output>30</output>

<result>30</result>