There are currently 23 students in Class 1 of the fifth grade. They want to participate in the activities. If there are no leftovers in groups of 3 or 5, at least how many students are needed?
五年级一班现有23名同学，他们想参加活动，分组时如果3人一个组或5人一个组都不剩余，至少还要几名同学？
<gadget id="calculator">30 - 23</gadget>
<output>7</output>

<result>7</result>