There are 10 red, yellow and blue balls of the same size and texture in the pocket. How many balls must be touched at a time to ensure that at least 4 balls have the same color.
口袋里有同样大小和同样质地的红、黄、蓝三种颜色的小球各10个．一次最少摸出多少个球，才能保证至少有4个球颜色相同．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<result>10</result>