To make a pair of cylindrical buckets without a lid with a base radius of 10 cm and a height of 40 cm, how many square centimeters of iron sheet should be at least?
做一对底面半径是10厘米、高40厘米的无盖圆柱形水桶，至少要铁皮多少平方厘米？
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">3.14 * 10 * 2 * 40</gadget>
<output>2_512</output>

<gadget id="calculator">314 + 2_512</gadget>
<output>2_826</output>

<gadget id="calculator">2_826 * 2</gadget>
<output>5_652</output>

<result>5_652</result>