Open in CoCalc with one click!

See http://www.sagemath.org/doc/reference/arithgroup/sage/modular/arithgroup/farey_symbol.html

FareySymbol(Gamma0(23)).fundamental_domain(tesselation='coset')
%time FareySymbol(Gamma0(389)).fundamental_domain(tesselation='coset')
CPU time: 5.49 s, Wall time: 7.89 s