import sys
import typing


def main() -> int:
    highest_seat = 0

    taken_seats = set()

    for line in sys.stdin:
        line = line.strip()
        if line == "":
            continue

        seat = _locate_seat(line)

        if seat.number > highest_seat:
            highest_seat = seat.number

        taken_seats.add(seat.number)

        print(f"bp={line} row={seat.row} column={seat.col} seat={seat.number}")

    seat_number: typing.Optional[int] = None
    n_found = 0

    for candidate_seat in range(0, (127 * 8) + 1):
        if candidate_seat in taken_seats:
            continue

        if (candidate_seat - 1) in taken_seats and (candidate_seat + 1) in taken_seats:
            seat_number = candidate_seat
            n_found += 1

    print(f"highest_seat={highest_seat} seat_number={seat_number} n_found={n_found}")

    return 0


class Seat:
    row: int
    column: int

    def __init__(self, row: int = 0, col: int = 0):
        self.row = row
        self.col = col

    @property
    def number(self) -> int:
        return (self.row * 8) + self.col


def _locate_seat(bp: str) -> Seat:
    rows = list(range(0, 128))
    cols = list(range(0, 8))

    row_part = list(bp[:7])
    col_part = list(bp[7:])

    return Seat(
        row=_bisect(rows, [{"F": 0, "B": 1}[s] for s in row_part]),
        col=_bisect(cols, [{"L": 0, "R": 1}[s] for s in col_part]),
    )


def _bisect(initial_selection: typing.List[int], bisections: typing.List[int]) -> int:
    selection = initial_selection[:]

    for bisection in bisections:
        halfway = int(len(selection) / 2)
        selection = [selection[:halfway], selection[halfway:]][bisection]

    return selection[0]


if __name__ == "__main__":
    sys.exit(main())