gap> c:=(5,1,2,3,4);
(1,2,3,4,5)
gap> a:=(5,6,2,1);
(1,5,6,2)
gap> b:=(2,6,4,3);
(2,6,4,3)
gap> g:=Group(a,b,c);
Group([ (1,5,6,2), (2,6,4,3), (1,2,3,4,5) ])
gap> Size(g);
120
gap> h:=EpimorphismFromFreeGroup(g:names:=["a","b","c"]);
[ a, b, c ] -> [ (1,5,6,2), (2,6,4,3), (1,2,3,4,5) ]
gap> PreImagesRepresentative(h,(4,5));
b*a^-1*b^-1*c
gap> PreImagesRepresentative(h,(3,4));
a^-1*b*a^-1*c*b
gap> PreImagesRepresentative(h,(2,3));
b*a^-1*b^-1
gap> PreImagesRepresentative(h,(4,6));
a^-2*b*a^-1*b^-2