There are 15 biscuits. The first person ate 1 yuan, and divided the rest equally between two people. The two people who got the biscuit ate one piece as before, and then divided it equally among the two people. The time to eat a biscuit is 1 minute, and the time of changing hands in the middle is not counted. There is no limit to the number of people who can eat cookies. How many minutes are the fastest to finish these biscuits?
有15块饼干．最开始的人吃了1块，把剩下的平分，分给了2个人．拿到饼干的2个人又像之前一样，吃了1块，然后分别平分给2个人．吃1块饼干的时间是1分钟，中间转手的时间不计．吃饼干的人数不限．这些饼干最快多少分钟吃完．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">15 - (1/2) - (1/2) - 1</gadget>
<output>13</output>

<gadget id="calculator">13 / 13</gadget>
<output>1</output>

<gadget id="calculator">1 + 1 + 1 + 1</gadget>
<output>4</output>

<result>4</result>