There is a piece of white paper in the shape of an isosceles trapezoid, with an upper base of 5 cm, a lower base of 13 cm, and a height of 6 cm. Cut out the largest circle from this piece of paper, how many square centimeters are left?
有一张等腰梯形的白纸，上底5cm，下底13cm，高6cm．从这张纸上剪下一个最大的圆，剩下的纸还有多少平方厘米？
<gadget id="calculator">5 + 13</gadget>
<output>18</output>

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

<gadget id="calculator">18 * 3</gadget>
<output>54</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">54 - 28.26</gadget>
<output>25.74</output>

<result>25.74</result>