cuboid carton with a square bottom, if you unfold its sides, you will get exactly a square with a side length of 40 cm. What is the surface area of this carton?
一个底面是正方形的长方体纸盒，如果把它的侧面展开，正好得到一个边长是40厘米的正方形．这个纸盒的表面积是多少？
<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">10 * 10 * 2</gadget>
<output>200</output>

<gadget id="calculator">40 * 40</gadget>
<output>1_600</output>

<gadget id="calculator">200 + 1_600</gadget>
<output>1_800</output>

<result>1_800</result>