Use a balance to weigh 4 times, how many table tennis balls can be found out of the only one that is unqualified due to overweight?
用一架天平称4次，最多能从多少个乒乓球中找出仅有的一个因超重原因不合格的乒乓球多少
<gadget id="calculator">3 ** 4</gadget>
<output>81</output>

<result>81</result>