A cylindrical tin bucket with a bottom but no cover is 6.28 decimeters high, and its side is just a square. How much iron is needed to make this tin bucket?
一只有底无盖的圆柱形铁皮桶，高为6.28分米，将它的侧面展开正好是正方形，做成这只铁皮桶至少需要多少铁皮？
<gadget id="calculator">6.28 * 6.28</gadget>
<output>39.4384</output>

<gadget id="calculator">6.28 / 3.14 / 2</gadget>
<output>1</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 1</gadget>
<output>3.14</output>

<gadget id="calculator">39.4384 + 3.14</gadget>
<output>42.5784</output>

<result>42.5784</result>