There are 10 red, yellow, blue, and white balls in each color, mix and put them in a cassette, at least how many balls can be drawn at a time, so as to ensure that there are 2 balls of the same color.
有红、黄、蓝、白四色小球各10个，混合放在一个暗盒里，一次至少摸出多少个，才能保证有2个小球是同色的．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>