A forest farm cuts down trees, transports them to a furniture factory, and stacks them layer by layer. Each layer has one tree less than the next layer, and the top layer has 4 trees stacked, making a total of 7 layers. How many trees have been felled in the forest farm?
某林场砍伐树木，运到家具厂将其逐层堆放，每层比下一层少一根，最上层堆放了4根，一共堆放了7层，林场一共砍伐了多少根树木？
<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">4 + 10</gadget>
<output>14</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">14 * (7/2)</gadget>
<output>49</output>

<result>49</result>