@Nullable
  private static Number getLastAddend(PsiPolyadicExpression polyadic) {
    if (polyadic != null) {
      int multiplier = getMultiplier(polyadic);
      if (multiplier != 0) {
        PsiExpression lastOp = ArrayUtil.getLastElement(polyadic.getOperands());
        Number lastAddend = getNumberFromLiteral(lastOp);
        if (multiplier == 1) {
          return lastAddend;
        }
        else if (multiplier == -1) {
          return negate(lastAddend);
        }
      }
    }
    return null;
  }
@Nullable
  private static Number getLastAddend(PsiPolyadicExpression polyadic)