4. <br /> 0 <br /> N <br /> 0 <br /> O <br /> O <br /> O <br /> 0 <br /> O <br /> O <br /> O <br /> O <br /> O <br /> O <br /> O <br /> U <br /> 0 <br /> ie <br /> 0 0 <br /> 0 <br /> CO <br /> N <br /> N <br /> O <br />