First. B and B start to climb the stairs from the first floor (the number of stairs between each two floors is the same), when A runs to the 4th floor, B happens to be on the 3rd floor, at this speed, A runs to the 16th floor How many floors does B go to when
甲．乙两人从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，乙跑到第多少层
<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>