How many boxes can the 25 balls be put into at most, in order to ensure that at least 2 balls can be found in a box.
把25个球最多只能放入多少个盒子中，才能保证一定能找到1个盒子里面至少有2个球．
<gadget id="calculator">25 - 1</gadget>
<output>24</output>

<result>24</result>