Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Critical charge of a system with one electron and five or six charged
  centers
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio