Two circles with a base radius of 1 cm and a rectangle with a length of 1 cm can enclose a cylinder.
两个底面半径1cm的圆和一个长多少cm的长方形可以围成一个圆柱．
<gadget id="calculator">2 * 3.14 * 1</gadget>
<output>6.28</output>

<result>6.28</result>