An opaque pocket contains 10 red, white, and yellow balls of the same size. At least how many balls must be touched to ensure that there are two balls of the same color.
一个不透明的口袋里有大小一样的红、白、黄三种颜色的小球各10个．至少要摸出多少个才能保证有两个球的颜色相同．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>