An ant crawls along the side of a rectangle with a length of 15 cm and a width of 12 cm. How many cm does it have to climb to get back to the starting point?
一只蚂蚁沿着一个长15厘米，宽12厘米的长方形的边爬行，它要爬多少厘米才能回到起点？
<gadget id="calculator">15 + 12</gadget>
<output>27</output>

<gadget id="calculator">2 * 27</gadget>
<output>54</output>

<result>54</result>