On Arbor Day, the fifth graders will participate in the tree planting activity. Each group will be divided into 15 or 18 people. They can be divided exactly. How many fifth graders will participate in the tree planting activity?
植树节，五年级同学参加种树活动，按每组15人或18人分，都能正好分完，参加植树活动的五年级同学至少有多少人．
<gadget id="calculator">2 * 3 * 3 * 5</gadget>
<output>90</output>

<result>90</result>