The length, width, and height of the candy box are 20cm, 15cm, and 6cm respectively. To pack two boxes of such candies into one package, at least how many square centimeters of wrapping paper is needed.
糖果盒的长、宽、高分别为20cm，15cm，6cm，将两盒这样的糖果包装成一包，至少需要多少平方厘米的包装纸．
<gadget id="calculator">20 * 15</gadget>
<output>300</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 * 2</gadget>
<output>2_040</output>

<gadget id="calculator">20 * 15 * 2</gadget>
<output>600</output>

<gadget id="calculator">2_040 - 600</gadget>
<output>1_440</output>

<result>1_440</result>