q = []


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(q)


def add(name):
    """Customer with name 'name' joining the queue"""
    q.append(name)


def next_():
    """Returns name of next customer to serve, removes customer from queue"""
    return q.pop(0)