Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Three real-space discretization techniques in electronic structure
  calculations
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess