square nursery with a side length of 15 meters, one side is against the wall, and three sides are surrounded by a fence. What is the length of the fence?
一块边长15米的正方形苗圃，一边靠墙，三边围上栅栏，栅栏长多少米．
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<result>45</result>