code: private int getOthers(IMolecularFormula formula) {
          int number = 0;
          String[] elements = {"Co", "Hg", "Pt", "As"};
          for (int i = 0; i < elements.length; i++)
              number += MolecularFormulaManipulator.getElementCount(formula,
                      formula.getBuilder().newInstance(IElement.class, elements[i]));
  
          return number;
      }
docs: Get the number of other elements which affect to the calculation of the nominal mass.
  For example Fe, Co, Hg, Pt, As.
  
  @param formula The IMolecularFormula to analyze
  @return        Number of elements