There is a cylindrical can with a height of 1 decimeter and a bottom circumference of 6.28 decimeters. How many square decimeters of iron sheet should be used for this box?
有一个圆柱形罐头盒，高是1分米，底面周长6.28分米，这个盒至少要用多少平方分米的铁皮．
<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 * 2</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 * 1</gadget>
<output>6.28</output>

<gadget id="calculator">6.28 + 6.28</gadget>
<output>12.56</output>

<result>12.56</result>