A cuboid iron bucket without a lid, the bottom is a square with side length 3 decimeters, and the height of the bucket is 0.5 meters. How many square decimeters of iron sheet is needed to do this at least?
一个无盖的长方体铁桶，底面是边长为3分米的正方形，桶高0.5米．做这个至少要用多少平方分米的铁皮？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">0.5 * 10</gadget>
<output>5</output>

<gadget id="calculator">3 * 5 * 4</gadget>
<output>60</output>

<gadget id="calculator">9 + 60</gadget>
<output>69</output>

<result>69</result>