Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: An extrapolation cascadic multigrid method combined with a fourth order
  compact scheme for 3D poisson equation
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an