@Nullable
    private static Integer getShift(int shiftForward, int shiftBackward) {
      if (shiftForward == -1 && shiftBackward == -1) return null;
      if (shiftForward == 0 || shiftBackward == 0) return 0;

      return shiftForward != -1 ? shiftForward : -shiftBackward;
    }
@Nullable
    private static Integer getShift(int shiftForward, int shiftBackward)