There are 3 red balls, 5 yellow balls, and 7 blue balls in a wooden box. If you touch the box blindfolded, how many balls should you take out at least to ensure that two of the balls you take out are of the same color?
木箱里装有红色球3个、黄色球5个、蓝色球7个，若蒙眼去摸，为保证取出的球中有两个球的颜色相同，则最少要取出多少个球？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>