One of the 9 parts is a defective product (the defective product is heavier), and the defective product can be found out at least as many times as we weigh it.
在9个零件里有1个是次品(次品重一些)，至少称多少次就一定能找出次品．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<result>2</result>