A square paper with a side length of 3 decimeters encloses a cylinder, what is its lateral area?
一张边长为3分米的正方形纸围成一个圆柱形纸筒，它的侧面积是多少平方分米．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>