def unique_activities_from_log(log, name_of_activity):
    """
    Returns unique activities from event log.
    :param name_of_activity: name of activity.
    :param log: event log.
    :return: unique activities.
    """

    unique_activities = []

    for sequence in log:
        for activity in sequence:
            unique_activities.append(activity[name_of_activity])

    return sorted(list(set(unique_activities)))