A box contains 5 red, yellow, and green balls each. How many balls must be taken out to ensure that there is 1 ball of each color.
一箱中装有红、黄、绿球各5个，至少取出多少个球，才能保证每种颜色的球各有1个．
<gadget id="calculator">5 + 5 + 1</gadget>
<output>11</output>

<result>11</result>