function W = solver(B)
[Brows Bcols] = size(B);
if Brows>8
    Brows = floor(Brows/4);
end

r1 = repmat([1:Brows],Bcols-1,1);
r1 = r1(:);

c1 = repmat([1:Bcols-1],Brows,1)';
c1 = c1(:);

r2 = r1;
c2 = c1+1;

W = [r1 c1 r2 c2];