Put 5 red, black, yellow and green colored balls of the same size in the pocket, at least how many balls can be drawn to ensure that there are two colored balls of the same color.
口袋里放红、黑、黄、绿四种颜色相同大小的彩球各5个，至少摸出多少个球，才能保证有两个同色的彩球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>