from datetime import datetime

def parking_fee(entry_time, exit_time):
    start = datetime.strptime(entry_time, "%H:%M")
    end   = datetime.strptime(exit_time, "%H:%M")

    elapsed_min = (end - start).total_seconds() // 60
    elapsed_min = int(elapsed_min)

    fee = 1000
    elapsed_min -= 30

    while elapsed_min > 0:
        fee += 500
        elapsed_min -= 10

    if fee > 20000:
        fee = 20000

    return fee

entry_time = "09:00"
exit_time  = "11:35"
ret = parking_fee(entry_time, exit_time)
print(ret)