function [ Y ] = invByNatalia( X )
%invByMatalia (X)
%   Calculate inverse of X, solving equation Xx = I

[r c] = size( X );

if (r == c)
    Z = [X eye(r, r)];

    for j=1:c-1
        for i=j+1:r
        Z(i,:) = Z(i,:) - Z(i,j)/Z(j,j) * Z(j,:);
        end
    end
    Y=Z;
else
   error('Error error');
end

end