gap> M:=ClosedSurface(2);;
gap> N:=SimplicialK3Surface();;
gap> W:=WedgeSum(M,N);;
gap> W:=RegularCWComplex(W);
Regular CW-complex of dimension 4

gap> W:=SimplifiedComplex(W);
Regular CW-complex of dimension 4

gap> cup:=CupProduct(W);;
gap> SecondCohomologyGens:=IdentityMat(23);;
gap> A:=NullMat(23,23);;
gap> for i in [1..23] do
> for j in [1..23] do
> A[i][j]:=cup(2,2,SecondCohomologyGens[i],SecondCohomologyGens[j])[1];
> od;od;
gap> Display(A);
[ [   -3,    1,    1,    0,    0,   -4,    1,    1,   -1,    2,    0,   -1,   -1,   -6,    0,    1,   -1,    1,   -1,    0,    1,   -2,    0 ],
  [    0,   -1,   -3,    2,   -2,    5,    0,    0,    0,   -1,    1,    0,    1,    6,    0,   -1,    0,   -1,    1,    0,   -1,    2,    1 ],
  [    0,   -1,   -2,    3,   -3,  -10,    0,    2,   -1,    1,    1,   -1,    2,    6,    1,   -1,    0,   -2,    1,   -2,   -3,    1,    0 ],
  [    2,    1,    2,  -10,    4,    7,    0,   -3,    0,   -2,   -1,    2,    0,    5,   -2,    0,    3,    2,    0,    3,    2,    0,    0 ],
  [    1,   -1,   -2,    4,   -2,   -4,    0,    2,    0,    0,    4,   -3,    2,   -9,    2,   -1,   -1,   -2,    1,   -4,   -1,    1,   -1 ],
  [   -1,   -4,   -6,    0,   -6,   -7,   -5,    7,   -9,   -2,   -7,    8,   -3,   54,   -8,   -5,    4,   -4,    5,   10,   -8,    6,   -4 ],
  [    1,    0,   -1,    0,   -1,    0,   -2,    1,    0,   -2,   -2,    2,    0,    7,   -2,   -1,    0,    0,    0,    2,   -1,    3,    1 ],
  [    0,    0,    0,   -2,    2,    3,    2,   -3,    1,    0,    0,    0,    0,    3,    1,    1,    1,    1,    0,    0,    1,   -1,    1 ],
  [    0,   -1,    0,   -2,   -2,   -4,   -3,    4,   -5,    1,   -2,    3,   -1,    9,   -4,   -3,    1,   -1,    1,    4,   -1,    1,   -3 ],
  [    1,    0,   -1,    0,    0,   -1,   -1,   -2,    2,   -2,   -1,    1,    0,    3,    0,    0,    1,    0,    0,    0,    0,    2,    2 ],
  [    0,    1,    2,   -1,   -1,  -16,   -3,    5,   -5,   -1,  -14,   11,   -3,   27,   -9,   -4,    5,   -3,    1,    8,   -7,    6,    0 ],
  [   -1,    2,    0,    0,    3,   21,    3,   -5,    7,    1,   11,  -10,    2,  -30,    7,    5,   -6,    4,   -2,   -6,    7,   -5,    1 ],
  [    0,    1,    2,    0,    0,   -5,    1,    0,    0,    0,    0,   -1,    0,   -8,    0,    1,    0,    0,   -1,   -2,    0,   -1,    1 ],
  [   -9,    3,    2,    3,   10,   58,    3,   -7,    6,    1,   -2,    3,  -11,  -22,    3,    7,   -4,    7,   -4,    5,   10,   -7,    5 ],
  [    1,   -1,    1,   -1,   -2,  -11,   -1,    4,   -5,    0,   -3,    2,    1,   14,   -4,   -3,    3,   -3,    2,    1,   -6,    1,   -2 ],
  [    1,   -1,   -1,    1,   -2,   -8,   -2,    3,   -3,    0,   -2,    3,    1,    7,   -2,   -4,    2,   -3,    2,    1,   -4,    2,   -1 ],
  [   -2,    1,   -1,    3,    0,    7,    1,   -1,    1,    1,    2,   -5,    0,   -8,    2,    3,   -4,    3,   -2,   -1,    2,   -2,    0 ],
  [    1,   -1,   -1,    2,   -2,   -4,   -2,    3,   -2,    0,   -1,    3,    0,    6,   -2,   -3,    2,   -4,    2,    0,   -4,    2,   -1 ],
  [   -1,    1,    1,    0,    2,    5,    0,   -1,    1,    0,    0,   -1,   -1,   -6,    1,    2,   -1,    2,   -2,    0,    2,   -1,    0 ],
  [    0,    1,   -1,    4,    1,   10,    1,   -2,    6,    0,    9,   -7,    2,  -29,    7,    3,   -5,    1,   -1,   -7,    5,   -2,    1 ],
  [    1,   -1,   -2,    2,   -4,  -12,   -2,    4,   -2,    0,   -4,    4,    0,   20,   -4,   -4,    2,   -4,    2,    2,   -6,    4,   -1 ],
  [   -1,    1,    2,   -3,    2,    6,    2,   -2,    1,    2,    4,   -3,    0,  -13,    2,    2,   -2,    2,   -1,   -1,    4,   -5,   -1 ],
  [    2,   -2,   -1,    0,   -3,  -11,   -1,    2,   -2,    0,    0,    0,    2,   10,   -1,   -1,    0,   -1,    0,    0,   -3,    1,   -3 ] ]
