gap> M:=ClosedSurface(2);;
gap> N:=SimplicialK3Surface();;
gap> W:=WedgeSum(M,N);
Simplicial complex of dimension 4.

gap> Cohomology(W,0);
[ 0 ]
gap> Cohomology(W,1);
[ 0, 0, 0, 0 ]
gap> Cohomology(W,2);
[ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]
gap> Cohomology(W,3);
[  ]
gap> Cohomology(W,4);
[ 0 ]
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);
[ [   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0 ],
  [   0,  -2,   2,  -1,   0,  -1,   1,  -1,   0,   0,   1,  -1,   0,   0,   1,   1,   2,  -1,  -1,   1,  -1,   0,  -1 ],
  [   0,   2,  -4,   2,  -1,   1,  -1,   1,   0,  -1,  -1,   0,   1,  -1,   1,  -1,  -2,   1,   2,  -2,   1,   0,   3 ],
  [   0,  -1,   2,  -2,   2,  -1,   0,  -1,   1,   1,   1,   0,   0,   0,  -2,   0,   0,   0,   0,   1,   0,   1,  -1 ],
  [   0,   0,  -1,   2,  -4,   1,   1,   1,  -2,  -1,  -1,   0,  -1,  -1,   4,   0,   1,  -1,  -1,  -1,  -1,  -1,   1 ],
  [   0,  -1,   1,  -1,   1,  -2,   0,  -1,   1,   0,   1,  -1,   1,   0,   0,   1,   1,   0,   0,   1,   0,   1,   0 ],
  [   0,   1,  -1,   0,   1,   0,  -2,   1,   0,   0,  -1,   0,   1,   1,  -1,   0,  -1,   0,   0,   0,   1,   0,   0 ],
  [   0,  -1,   1,  -1,   1,  -1,   1,  -2,   1,   0,   1,  -1,   1,   0,   0,   1,   1,   0,   0,   1,   0,   0,   0 ],
  [   0,   0,   0,   1,  -2,   1,   0,   1,  -2,  -1,   0,   0,  -1,  -1,   2,   0,   0,  -1,   0,  -1,  -1,  -1,   0 ],
  [   0,   0,  -1,   1,  -1,   0,   0,   0,  -1,  -2,   0,  -1,   0,   0,   2,   1,   0,   0,   0,   0,   0,  -1,   1 ],
  [   0,   1,  -1,   1,  -1,   1,  -1,   1,   0,   0,  -2,   0,   1,   1,  -1,   0,  -1,   0,   0,   0,   1,  -1,   0 ],
  [   0,  -1,   0,   0,   0,  -1,   0,  -1,   0,  -1,   0,  -2,   1,   0,   2,   1,   1,  -1,   0,   0,   0,   0,   1 ],
  [   0,   0,   1,   0,  -1,   1,   1,   1,  -1,   0,   1,   1,  -2,   0,   0,   0,   0,   1,  -1,   1,  -1,  -1,  -2 ],
  [   0,   0,  -1,   0,  -1,   0,   1,   0,  -1,   0,   1,   0,   0,  -2,   3,   0,   1,  -1,   0,  -1,  -1,   0,   1 ],
  [   0,   1,   1,  -2,   4,   0,  -1,   0,   2,   2,  -1,   2,   0,   3,  -8,  -1,  -2,   1,   1,   1,   2,   0,  -2 ],
  [   0,   1,  -1,   0,   0,   1,   0,   1,   0,   1,   0,   1,   0,   0,  -1,  -2,  -1,   1,   1,  -1,   0,   0,   0 ],
  [   0,   2,  -2,   0,   1,   1,  -1,   1,   0,   0,  -1,   1,   0,   1,  -2,  -1,  -2,   0,   2,  -1,   1,   0,   0 ],
  [   0,  -1,   1,   0,  -1,   0,   0,   0,  -1,   0,   0,  -1,   1,  -1,   1,   1,   0,  -2,  -1,   0,   0,  -1,   1 ],
  [   0,  -1,   2,   0,  -1,   0,   0,   0,   0,   0,   0,   0,  -1,   0,   1,   1,   2,  -1,  -2,   1,  -1,   0,  -2 ],
  [   0,   1,  -2,   1,  -1,   1,   0,   1,  -1,   0,   0,   0,   1,  -1,   1,  -1,  -1,   0,   1,  -2,   0,  -1,   2 ],
  [   0,  -1,   1,   0,  -1,   0,   1,   0,  -1,   0,   1,   0,  -1,  -1,   2,   0,   1,   0,  -1,   0,  -2,   0,   0 ],
  [   0,   0,   0,   1,  -1,   1,   0,   0,  -1,  -1,  -1,   0,  -1,   0,   0,   0,   0,  -1,   0,  -1,   0,  -2,   1 ],
  [   0,  -1,   3,  -1,   1,   0,   0,   0,   0,   1,   0,   1,  -2,   1,  -2,   0,   0,   1,  -2,   2,   0,   1,  -4 ] ]
