function BIA=bialt(A)


n = length(A);
B = eye(n);

BIA = zeros( (n*(n-1)) / 2);
N = 0;
N1 = 0;
N2 = 0;
N3 = 0;
N4 = 0;

for i=2:1:n
    for j=1:1:(i-1)
        for k=2:1:n
            for l=1:1:(k-1)
                I1 = 0.5*(i-1)*(i-2) + j;
                I2 = 0.5*(k-1)*(k-2) + l;         
                BIA( I1, I2 ) = 0.5*(det([ A(i,k) A(i,l) ; B(j,k) B(j,l)]) + det( [ B(i,k) B(i,l); A(j,k) A(j,l)]) );
            end
        end
    end
end
