parking_lot

parking_lot = set()
while True:
    command = input().split(', ')
    if command[0] == 'END':
        break

    direction, car_number = command
    if direction == 'IN':
        parking_lot.add(car_number)
    else:
        parking_lot.remove(car_number)

if parking_lot:
    [print(car) for car in parking_lot]
else:
    print('Parking Lot is Empty')