Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Magnetic force microscopy measurement of the penetration depth in
  superconductors from Meissner repulsion
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg