A classroom with a length of 15 meters, a width of 8 meters, and a height of 4 meters is used to paint the roof and four walls. 1.5 kilograms of paint are used per square meter, except for doors, windows, and blackboards, which cover an area of 24 square meters. How many kilograms of paint should be prepared to paint this classroom?
一间长15米，宽8米，高4米的教室，粉刷其屋顶及四面墙壁，每平方米用涂料1.5千克，除门窗、黑板面积24平方米，粉刷这间教室要准备多少千克涂料？
<gadget id="calculator">15 * 8</gadget>
<output>120</output>

<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">4 * 15</gadget>
<output>60</output>

<gadget id="calculator">120 + 32 + 60</gadget>
<output>212</output>

<gadget id="calculator">212 * 2</gadget>
<output>424</output>

<gadget id="calculator">424 - 120 - 24</gadget>
<output>280</output>

<gadget id="calculator">280 * 1.5</gadget>
<output>420</output>

<result>420</result>