There are 10 red, yellow, blue and green balls in the bag (the balls are exactly the same except for the color), and one is taken at a time. If it is guaranteed that there must be three balls of the same color, how many balls should be taken at least? indivual.
袋子里装有红，黄，蓝，绿四种颜色的小球各10个(小球除颜色外完全相同)，每次取一个，若保证取出的球中必须有三个同色，那至少取出多少个．
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">8 + 1</gadget>
<output>9</output>

<result>9</result>