There are many glass beads of the same specification but different colors in a bag. The colors are red, yellow, blue, and green. How many beads must be taken at least to ensure that there are 2 of the same color.
一只袋中装有许多规格相同但颜色不同的玻璃珠，颜色有红、黄、蓝、绿四种，最少要取出多少个珠子才能保证有2个同色的．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>