There are a pile of steel pipes, stack them into an isosceles trapezoid, there are 15 steel pipes in the top layer, one more than the layer above it in each layer from the bottom, and 28 steel pipes in the bottom layer, how many steel pipes are there in this pile?
有一堆钢管，把它堆成一个等腰梯形，最上层有15根，下面开始每层都比它上面一层多一根，最下层28根，这堆钢管一共有多少根？
<gadget id="calculator">15 + 28</gadget>
<output>43</output>

<gadget id="calculator">28 - 15</gadget>
<output>13</output>

<gadget id="calculator">13 + 1</gadget>
<output>14</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">43 * 7</gadget>
<output>301</output>

<result>301</result>