There is a square handkerchief with a side length of 15 centimeters. It is necessary to embroider lace around it. What is the length of the lace in centimeters?
有一块正方形的手绢边长15厘米，要在它四周绣上花边，花边的长是多少厘米？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<result>60</result>