Sew lace around the sides of a square tablecloth with a side length of 20 decimeters. What is the total length of the lace?
给一个边长是20分米的正方形桌布四周缝上花边，花边的总长是多少分米．
<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>