Set a border around a square landscape painting with a side length of 5 decimeters. What is the total length of the border in decimeters?
给一幅边长5分米的正方形风景画四周订上边框，边框的总长是多少分米．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>