There are 18 female students, and 2 male students are inserted between each 2 female students, how many male students are needed?
有18名女同学，每2名女同学之间插入2名男同学，需多少男同学？
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">17 * 2</gadget>
<output>34</output>

<result>34</result>