6 glass balls of red, white, yellow, and black colors are placed in a bag. Take the balls with your eyes closed, at least how many balls you take, you can guarantee to get two balls of the same color.
红、白、黄、黑四种颜色的玻璃球各6个放到一个袋里．闭着眼睛从中取球，至少取多少个球，可以保证取到两个颜色相同的球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>