A piece of rectangular paper is folded in half in the same direction, folded in half, folded in half again...how many rectangles are there when folded in half 4 times?
一张长方形纸向同方向对折，对折，再对折…对折4次有多少长方形．
<gadget id="calculator">2 * 2 * 2 * 2</gadget>
<output>16</output>

<result>16</result>