There are 12 red, yellow, and blue balls of the same size in the box, and there must be 2 balls of the same color if you want to draw the balls. At least how many balls must be drawn.
盒子里有同样大小的红、黄、蓝三种颜色的球各12个要想摸出的球一定有2个同色的，至少要摸出多少个球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>