March 12th is Arbor Day. The school organizes fifth graders to plant trees. They can be divided into groups of 15 or 18. How many people are there to participate in the tree planting?
3月12日是植树节，学校组织五年级同学去植树，按15人或18人一组都能正好分完，参加植树至少有多少人？
<gadget id="calculator">2 * 3 * 3 * 5</gadget>
<output>90</output>

<result>90</result>