There are 5 red balls and 4 white balls in a box, one ball is taken out at a time, how many times can the red ball be guaranteed at most.
盒子里装有5个红球，4个白球，一次取出一个球，最多多少次能保证拿到红球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>