To pack three identical school books with length, width and height of 20 centimeters, 15 centimeters and 2 centimeters into a package, what is the minimum area of wrapping paper needed? (not counting joints)
把3本长、宽、高分别是20厘米、15厘米、2厘米的同样的书包成一包，至少需要多大面积的包装纸？(接头处不计)
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">20 * 6</gadget>
<output>120</output>

<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">300 + 120 + 90</gadget>
<output>510</output>

<gadget id="calculator">510 * 2</gadget>
<output>1_020</output>

<result>1_020</result>