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what even are these symbols?

Source: 2023 Olympic Revenge problem 6

March 28, 2023
group theoryrandomalgebra

Problem Statement

We say that HH permeates GG if GG and HH are finite groups and for all subgroup FF of GG there is HHH'\cong H with HFH'\le F or FHGF\le H'\le G. Suppose that a non-abelian group HH permeates GG and let S=HGHHS=\langle H'\le G | H'\cong H\rangle. Show that HSH>1|\bigcap_{H'\in S} H'|>1