A monthly calendar, each 5 decimeters long and 4 decimeters wide. How many square decimeters of paper does this calendar use at least?
每月一张的挂历，每张长5分米，宽4分米．这本挂历至少用纸多少平方分米？
<gadget id="calculator">5 * 4 * 12</gadget>
<output>240</output>

<result>240</result>