There is a pile of logs, and there are 10 logs in the bottom layer. When stacking upwards, put 1 log less in each layer. There are 5 layers in total. How many logs are there in this pile?
有一堆圆木，最下层有10根，向上堆的时候，每层依次少放1根，一共放了5层，这堆圆木共有多少
<gadget id="calculator">10 - 5</gadget>
<output>5</output>

<gadget id="calculator">5 + 1 + 10</gadget>
<output>16</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">16 * (5/2)</gadget>
<output>40</output>

<result>40</result>