Suppose I have a discrete set $A=\{a_1,\ldots,a_k\}$ and I wish to write an expression for the minimum of this set. I would write:
$$ \min \{a_1,\ldots,a_k\} $$
But what if rather than just an element, I want the subset of $A$ containing the $n$ smallest elements of $A$? How would I write that?