Master Wang wants to use iron sheets to make an uncovered bucket with a bottom radius of 2 decimeters and a height of 4 decimeters. How much iron sheet is needed at least?
王师傅要用铁皮做一只底面半径是2分米，高4分米的无盖水桶，至少需要多少铁皮？
<gadget id="calculator">2 * 3.14 * 2 * 4</gadget>
<output>50.24</output>

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

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

<gadget id="calculator">50.24 + 12.56</gadget>
<output>62.8</output>

<result>62.8</result>