To make 4 cylindrical oil barrels, the radius of the bottom surface is 3 decimeters, and the height is 0.8 meters. How many square decimeters of iron sheet are needed at least?
制作4个圆柱形油桶，底面半径是3分米，高是0.8米，至少需要多少平方分米铁皮？
<gadget id="calculator">2 * 3.14 * 3 * 0.8 * 10</gadget>
<output>150.72</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9 * 2</gadget>
<output>56.52</output>

<gadget id="calculator">150.72 + 56.52</gadget>
<output>207.24</output>

<gadget id="calculator">207.24 * 4</gadget>
<output>828.96</output>

<result>828.96</result>