In a parallelogram, the lengths of two sides are 8 cm and 5 cm respectively. What is the perimeter of this parallelogram
在一个平行四边形里，其中两条边的长度分别是8厘米和5厘米．这个平行四边形的周长是多少
<gadget id="calculator">8 + 5</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>