The national flag displayed by Chinese astronaut Yang Liwei in space is 15 centimeters long and 10 centimeters wide. What is the circumference of the national flag in centimeters?
中国航天员杨利伟在太空展示的国旗，长15厘米，宽10厘米，这面国旗的周长是多少厘米．
<gadget id="calculator">15 + 10</gadget>
<output>25</output>

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

<result>50</result>