function [ r ] = orizousa( D )
%computes orizousa
s=size(D);
    if s(1)~=2||s(2)~=2
        r=NaN;
        disp('non 2x2 matrix');
    else
        r=D(1,1)*D(2,2)-D(1,2)*D(2,1);
    end
end

