There are 4 red balls and 3 yellow balls in the box, one ball is taken out at a time, how many times can the red ball be guaranteed at least.
盒里装着4个红球和3个黄球，一次取出一个球，最少多少次能保证拿到红球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>