The acquisition station has a pile of logs, and each level of it has one less than the next level. Xiao Min counted, and the bottom layer is 26, and there are 18 layers in total. Do you know how many logs are in the top layer of this pile of logs.
收购站有一堆圆木，它的每一层都比下一层少一根．小敏数了数，它的最下一层是26根，一共有18层．你知道这堆圆木最上一层多少根．
<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">1 * 17</gadget>
<output>17</output>

<gadget id="calculator">26 - 17</gadget>
<output>9</output>

<result>9</result>