Use a pan to fry fish, only 2 fish can be fried at a time, and it takes 2 minutes to fry a fish (1 minute for the front and 1 minute for the back). If you want to fry 13 fish, how many minutes will it take at least?
用一只平底锅煎鱼，每次只能煎2条，煎一条鱼需要2分钟(正、反面各需1分钟)．如果要煎13条鱼，最少需要多少分钟．
<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">10 + 3</gadget>
<output>13</output>

<result>13</result>