There are balls of four colors in a black pocket. There are enough balls of each color. Their shapes and sizes are all the same, but their colors are different. How many balls must be taken out at a time to ensure that at least 5 of them have the same color.
一只黑色口袋里有四种颜色的球，每种颜色的球足够多个，它们的形状，大小都相同，只是颜色不同．一次至少取出多少个，才能保证其中至少有5个球的颜色相同．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<result>17</result>