"""
 looking at the babysitting problem in class
"""

def calc_money(start, end):
    """ Return amount of money charged. """
    rate_switch_time = 9  # 9:00pm
    high_rate = 2.50      # $ per hour
    low_rate = 1.75       # $ per hour
    if end > rate_switch_time and start >= rate_switch_time:
        high_hours = end - start
        low_hours = 0
    elif end > rate_switch_time and start < rate_switch_time:
        high_hours = end - rate_switch_time
        low_hours = rate_switch_time - start
    else:
        high_hours = 0
        low_hours = end - start
    return high_rate * high_hours + low_rate * low_hours

def time_to_hours(hr_min):
    """ Convert a time like '10:23' to fractional hours,
        with times after midnight continuing past 12,
        i.e. 2:34 is 14+(34/60.0)
    """
    earliest_time = 4   # times earlier than 4:00 are am
    import string
    strings = string.split(hr_min, ':')  #  ['10', '23']
    # print "strings = ", strings
    hour = int(strings[0]) + int(strings[1])/60.0
    # print "hour = ", hour
    if (hour < earliest_time):
        hour = hour + 12
    # print "hour = ", hour
    return hour

def main():
    print "babysit"
    start = time_to_hours(raw_input("start time = ? (hh:mm) "))
    # print "start = ", start
    end = time_to_hours(raw_input("end time = ? (hh:mm) "))
    # print "end = ", end
    print "the amount is $%0.2f " % calc_money(start, end)
    

main()