gap> qL:=IntersectionForm(L);;
gap> qM:=IntersectionForm(M);;
gap> qN:=IntersectionForm(N);;
gap> Display(qL);
[ [  -2,   1 ],
  [   1,   0 ] ]
gap> Display(qM);
[ [  5,  2 ],
  [  2,  1 ] ]
gap> Display(qN);
[ [  -3,  -2 ],
  [  -2,  -1 ] ]
