A classroom is 8 meters long, 5 meters wide, and 4 meters high. It is necessary to paint the top surface and surrounding walls of the classroom, and remove 20 square meters of doors, windows and blackboards. How many square meters is the painted area?
一个教室长8米，宽5米，高4米．要粉刷教室的顶面和四周墙壁，除去门窗黑板20平方米．粉刷的面积是多少平方米？
<gadget id="calculator">8 * 5</gadget>
<output>40</output>

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

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">32 + 20</gadget>
<output>52</output>

<gadget id="calculator">52 * 2</gadget>
<output>104</output>

<gadget id="calculator">104 - 20</gadget>
<output>84</output>

<gadget id="calculator">40 + 84</gadget>
<output>124</output>

<result>124</result>