There is a square flower bed in the park in the middle of the street. There are 15 potted flowers on each side of the outermost layer, and how many potted flowers are placed on the outermost layer.
街心公园有一个方形花坛，最外层每边各摆15盆花，最外层摆了多少盆花．
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">60 - 4</gadget>
<output>56</output>

<result>56</result>