A and B start to climb the stairs from the ground floor (the first floor) (the number of stairs between each two floors is the same). When A runs to the fourth floor, B happens to be on the third floor. At this speed, A When running to the 16th floor, how many floors does B go to?
甲、乙二人从底楼(第一层)开始比赛爬楼梯(每两层之间楼梯的级数相同)甲跑到第4层时，乙恰好到第3层，照这样的速度，甲跑到第16层时，乙跑到多少层．
<gadget id="calculator">16 - 1</gadget>
<output>15</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">1 / (3/2)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">15 * (2/3)</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>