Xiao Ming wants to inlay a square handkerchief with lace. Each side of the handkerchief is 20 cm long. How many centimeters of lace is needed to inlay the lace?
小明要给一个正方形的手帕镶花边，手帕每条边长20厘米，要想把花边镶好，需要花边几厘米？
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>