q = []
# n = 0   # number of people in the queue


def length():
    """Returns number of waiting customers"""
    return len(q)


def show():
    """SHOW queue: print list of waiting customers.
    Customer waiting longest
    are shown at the end of the list."""
    print(list(reversed(q)))


def add(name):
    """Customer with name 'name' joining the queue"""
    # could check that name is a string
    q.append(name)


def next():
    """Returns name of next customer to serve,
    removes customer from queue"""
    if len(q) == 0:
        print("The queue is empty.")
    else:
        return q.pop(0)