The sum of the interior angles of a polygon is 540°, how many polygons is it?
一个多边形的内角和是540°，它是多少边形．
<gadget id="calculator">540 / 180</gadget>
<output>3</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<result>5</result>