To cut 3 circular pieces of paper with a radius of 2 decimeters, at least a rectangular piece of paper with an area of square decimeters must be prepared.
要剪3个半径为2分米的圆形纸片，至少要准备面积是多少平方分米的长方形纸片．
<gadget id="calculator">2 * 6</gadget>
<output>12</output>

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

<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<result>48</result>