sheep is tied to a vertex of a square building by a 30-meter-long rope. The side length of the building is 20 meters, surrounded by grassland. How many square meters of grassland can this sheep eat?
一只羊被30米长的绳子拴在了正方形建筑物的一个顶点上，建筑物的边长是20米，周围全是草地，这只羊能吃到草的草地面积是多少平方米？
<gadget id="calculator">30 ** 2</gadget>
<output>900</output>

<gadget id="calculator">360 - 90</gadget>
<output>270</output>

<gadget id="calculator">270 / 360</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">3.14 * 900 * (3/4)</gadget>
<output>2_119.5</output>

<gadget id="calculator">30 - 20</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">90 / 360</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3.14 * 100 * (1/4) * 2</gadget>
<output>157</output>

<gadget id="calculator">2_119.5 + 157</gadget>
<output>2_276.5</output>

<result>2_276.5</result>