rowCount = 10
rowSeats = "AB-CDF-GH"

desiredSeats = 2

occupied = set()  # "1A", "1C"

for seat in "1A, 1C, 2D, 2F".split():
    occupied.add(seat)

for row in range(1, rowCount+1):

    available = []

    for seat in rowSeats:
        seatID = "%s%s" % (row, seat)
        if seatID in occupied or seat == "-":
             available = []
             continue

        available.append(seatID)

        if len(available) == desiredSeats:
            for seat in available:
                occupied.add(seat)

            print("found seats: %s" % ", ".join(available))