There are 3 classes of students in the fifth grade of our school participating in today's math competition. At least how many people are selected to ensure that there are 4 students in the same class.
我校五年级有3个班的学生参加今天的数学竞赛，至少有多少人被选上才能保证有4名同学同班．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

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

<result>10</result>