There are 9 blue balls, 5 black balls, 6 white balls and 3 red balls in a box. If you close your eyes and touch the balls from the box, you are only allowed to touch one ball at a time. At least two of the balls drawn are the same color?
一个盒子里有9个蓝球、5个黑球、6个白球和3个红球，如果闭上眼睛，从盒子中摸球，每次只许摸一个球，至少要摸出多少个才能保证摸出的这几个球中至少有两个颜色相同？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>