Draw the largest circle in a square. The circumference of this circle is 6.28 cm. What is the area of this square in square centimeters?
在一个正方形里面画一个最大的圆，这个圆的周长是6.28厘米，这个正方形的面积是多少平方厘米．
<gadget id="calculator">6.28 / 3.14</gadget>
<output>2</output>

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

<result>4</result>