There is a pile of wood, the bottom layer is 15, each layer is reduced by 1, and the top layer is 4, how many logs are there in this pile?
有一堆木料，最下面一层是15根，每上一层减少1根，最上面一层是4根，这一堆木料一共有多少根？
<gadget id="calculator">15 + 4</gadget>
<output>19</output>

<gadget id="calculator">15 - 4</gadget>
<output>11</output>

<gadget id="calculator">11 + 1</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">19 * 6</gadget>
<output>114</output>

<result>114</result>