Stack 105 pieces of wood in 6 layers. When stacking, if each time the upper layer of wood is one less than the lower layer of wood, how many pieces should be placed in the bottom layer.
把105根木材按6层堆积起来，堆积的时候，若每次上层木材比下层木材少一根，则最下层应放多少根．
<gadget id="calculator">2 / 6</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">105 * (1/3)</gadget>
<output>35</output>

<gadget id="calculator">35 + 5</gadget>
<output>40</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<result>20</result>