There are 4 yellow balls and 4 white balls in the box. How many balls must be drawn at a time to ensure that there are both yellow balls and white balls.
盒子中有4个黄球和4个白球，一次至少摸出多少个，才能保证摸出的球中既有黄球也有白球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>