Use a pan to pancake, you can bake up to 2 cakes at a time, and bake both sides for 2 minutes on each side. If you want to bake 9 cakes, how many minutes will it take at least?
用平底锅烙饼，每次最多可以烙2张饼，两面都要烙，每面2分钟．如果要烙9张饼，最少需要多少分钟．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">2 * 2 * 3</gadget>
<output>12</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">12 + 6</gadget>
<output>18</output>

<result>18</result>