The fifth grade students participate in the tree planting labor, and they are divided into groups of 15 or 18. At least how many people in the fifth grade participate in tree planting?
五年级同学参加植树劳动，按15人一组或18人一组都正好分完．五年级同学参加植树的至少有多少人？
<gadget id="calculator">2 * 3 * 3 * 5</gadget>
<output>90</output>

<result>90</result>