A small square blackboard with a side length of 5 decimeters, how long the wooden strips are needed to inlay wooden strips around the small blackboard?
一块边长5分米的正方形小黑板，给这块小黑板四周镶上木条，需要多长的木条？
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>