In a pile of steel pipes, there are 2 steel pipes in the uppermost layer, 12 steel pipes in the lowermost layer, and the difference between two adjacent layers is 1 steel pipe. How many steel pipes are there in total in this pile?
一堆钢管，最上层有2根，最下层有12根，相邻两层相差1根，这堆钢管一共有多少根．
<gadget id="calculator">2 + 12</gadget>
<output>14</output>

<gadget id="calculator">12 - 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">14 * (11/2)</gadget>
<output>77</output>

<result>77</result>