Wang Hua wants to cut a circular piece of paper with a circumference of 6.28 cm. How many square centimeters of square paper does he need at least?
王华想要剪一个周长是6.28厘米的圆形纸片，他至少要多少平方厘米的正方形纸片？
<gadget id="calculator">6.28 / 3.14</gadget>
<output>2</output>

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

<result>4</result>