A pile of cylindrical wood, put 1 on the top layer, put 2 more than the upper layer on each lower layer, and put 19 logs on the bottom, how many logs are there in total in this pile.
一堆圆柱形木材，最上层放1根，往下每层比上层多放2根，最下面放了19根，这堆木材共有多少根．
<gadget id="calculator">1 + 19</gadget>
<output>20</output>

<gadget id="calculator">19 - 1</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<result>100</result>