There are 2 red, 2 white and 2 yellow table tennis balls in the box. You don’t need to reach out to touch the balls. How many balls can be touched to ensure that there is at least one white table tennis ball.
箱子中有红、白、黄色乒乓球各2个，不用眼看伸手去摸球，摸出多少个球才能保证至少有一个白色乒乓球．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>