There are several small balls of 4 colors in the box, as many as you take at a time, there must be two small balls of the same color.
盒子里有4种颜色的小球若干个，一次拿多少个就一定有两个小球同色．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>