In a pile of wood, there are 8 roots in the bottom layer and 1 root in the top layer, and there is a difference between two adjacent layers. What is the total number of logs in this pile?
一堆木料，最下层有8根，最上层有1根，每相邻两层都相差一根，这堆木料的总根数是多少
<gadget id="calculator">1 + 8</gadget>
<output>9</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>