There are 4 white, black, red, and yellow balls of the same size, and at least how many balls are drawn each time to ensure that there are 2 balls of the same color.
有白、黑、红、黄四色大小一样的小球各4个，每次至少摸出多少个，才能保证有2个相同颜色的小球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>