The off-campus counselor Xiao Wang and all the students in Class 4 and Class 2 stood in a row to report the number. Counting from left to right, reporting to 15 is the counselor; reporting from right to left, reporting to 17 is the counselor. Then how many students are there in Class 4 and Class 2?
校外辅导员小王和四2班全体同学站成一排报数．从左向右报数，报到15是辅导员；从右向左报数，报到17是辅导员．则四2班共有学生多少人．
<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">17 - 1</gadget>
<output>16</output>

<gadget id="calculator">14 + 16</gadget>
<output>30</output>

<result>30</result>