Among the students in Class 1, the oldest is 13 years old, and the youngest is 11 years old. At least how many students need to be selected from them, so that at least two of the selected students will be of the same age.
六1班学生中年龄最大的是13岁，最小的是11岁．至少需要从中挑选多少名同学，就一定能使挑出的同学中至少有两名同学岁数相同．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>