210 bricks are stacked into 15 layers, so that each layer has one brick less than the next layer, so what is the number of bricks in the bottom layer
将210块砖堆成15层，使每层都比下一层少一块砖，那么最下层的砖的块数为多少
<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">14 * (15/2)</gadget>
<output>105</output>

<gadget id="calculator">210 - 105</gadget>
<output>105</output>

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

<gadget id="calculator">105 / 15</gadget>
<output>7</output>

<gadget id="calculator">15 - 1</gadget>
<output>14</output>

<gadget id="calculator">14 * 1</gadget>
<output>14</output>

<gadget id="calculator">7 + 14</gadget>
<output>21</output>

<result>21</result>