A cylindrical tea canister with a diameter of 4 cm is placed on a table, what is the area covered by the table in square centimeters?
一个直径4厘米的圆柱体茶叶筒放在桌面上，桌面被遮住的面积是多少平方厘米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>