There are some mooncakes in the store, and a box of 6 yuan or a box of 9 yuan is just finished. How many mooncakes are there at least?
商店里有一些月饼，6块一盒或9块一盒都正好装完，这些月饼至少有多少块？
<gadget id="calculator">2 * 3 * 3</gadget>
<output>18</output>

<result>18</result>