How many square centimeters of iron sheet should be used to make a cylinder whose base radius is 50 centimeters and whose length is 200 centimeters?
制作一个底面半径是50厘米，长是200厘米的圆柱体的通风管，至少要用多少平方厘米的铁皮？
<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 200</gadget>
<output>62_800</output>

<result>62_800</result>