The fifth grade students go rowing, 4 people row a boat and there are 3 people, and 6 people row a boat and there are 3 people. How many students are there at least to participate in rowing?
五年级同学去划船，4人划一只船余3人，6人划一只船也余3人．参加划船的同学至少有多少人？
<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<result>15</result>