Put 7 red balls and 4 basketballs of the same size into a pocket. At least how many balls must be drawn in the dark to ensure that two balls are of different colors.
把同样大小的7个红球和4个篮球放进一个口袋里．黑暗中至少摸出多少个球，才能保证有两个球是不同色的．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<result>8</result>