There are 12 logs in the lower layer and 7 logs in the upper layer. There are 6 layers in the pile. How many logs are there in this pile?
一堆圆木，堆成梯形状，下层12根，上层7根，共堆有6层，这堆圆木共有多少根．
<gadget id="calculator">12 + 7</gadget>
<output>19</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">19 * 3</gadget>
<output>57</output>

<result>57</result>