You can only put 2 pancakes in a pan at a time, and it takes 2 minutes to fry one pancake (1 minute on each side of the front and back), and how many minutes does it take to fry 7 pancakes at least.
用一个平底锅煎饼每次只能放2张，煎一张需要2分钟(正反两面各1分钟)，煎7张饼至少需要多少分钟．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<result>7</result>