Use a pan to make pancakes, and you can put 2 pancakes at the same time. If it takes 2 minutes to fry a pancake, assuming that the front and back sides need 1 minute each, find out how many minutes it will take to fry 7 pancakes.
用一只平底锅煎饼，每一次能同时放2只饼，如果煎一个饼需要2分钟，假定正反面各需要1分钟，求煎7只饼至少要多少分钟．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

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

<result>7</result>