An ant crawls along the side of a rectangle with a length of 15 cm and a width of 10 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10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 + 10</gadget>
<output>25</output>

<gadget id="calculator">2 * 25</gadget>
<output>50</output>

<result>50</result>