Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: On the number of crossings in a random labelled tree with vertices in
  convex position
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom