In the middle of a rectangular square with a length of 15 meters and a width of 12 meters, there are many seaweeds hanging to dry, forming a circle with a radius of 4 meters. How much area of this square is useless?
在一个长15米，宽12米的长方形广场中间，晾着许多海带，组成了一个半径是4米的圆形，这个广场还有多大面积没有用？
<gadget id="calculator">15 * 12</gadget>
<output>180</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<gadget id="calculator">180 - 50.24</gadget>
<output>129.76</output>

<result>129.76</result>