def proportion_of_traffic_from_top_users(tweets, users_with_freq, n):
    
    """
    Return the percentage of the traffic that comes from the n most active accounts in a list of tweets.

    :param tweets: the list of tweets, represented as dictionaries.
    :param users_with_freq: a Counter of usernames with the number of tweets in 'tweets' from each user.
    :param n: number of most active users to be considered.

    :return: float. percentage of the traffic that comes from the top n most active users in 'tweets'
    """

    total_traffic = len(tweets)
    top_users = users_with_freq.most_common(n)

    traffic_from_top_users = 0

    for (user, freq) in top_users:
        traffic_from_top_users += freq

    return (traffic_from_top_users/total_traffic)*100