def calculate_simil(word1: str, word2: str):
    score = 0
    if word1[0] == word2[0]:
        score += 10
    if word1[-1] == word2[-1]:
        score += 10
    length_of_word1 = len(word1)
    length_of_word2 = len(word2)
    score += (length_of_word1 / length_of_word2) * 30 \
        if (length_of_word1 <= length_of_word2) \
        else (length_of_word2 / length_of_word1) * 30
    uniques = ''.join(set(word1 + word2))
    commons = ''.join(set(word1).intersection(word2))
    score += (len(commons) / len(uniques)) * 50

    return score


def get_max_score_in_words_list(lists):
    current_max = 0
    for score in lists.values():
        current_max = max([current_max, score])

    maxes = []
    for word, score in lists.items():
        if score == current_max:
            maxes.append(word)

    return maxes


def calculate_scores(words):
    scores = {}
    for word in words:
        scores[word] = []
    i = 0
    for word1 in words:
        j = 0
        for word2 in words:
            if i == j:
                continue
            score = calculate_simil(word1, word2)
            scores[word1].append(score)
            scores[word2].append(score)
            j += 1
        i += 1

    return scores


def calculate_average(scores):
    avgs = {}
    for word, score in scores.items():
        avgs[word] = sum(score) / len(score)
    return avgs


def find_word(message):
    words = "".join((char.lower() if char.isalpha() else " ") for char in message).split()
    scores = calculate_scores(words)
    avgs = calculate_average(scores)
    max_words = get_max_score_in_words_list(avgs)

    if len(max_words) == 1:
        return max_words[0]

    for word in reversed(words):
        if word in max_words:
            return word


if __name__ == '__main__':
    # These "asserts" using only for self-checking and not necessary for auto-testing
    assert find_word("Speak friend and enter.") == "friend", "Friend"
    assert find_word("Beard and Bread") == "bread", "Bread is Beard"
    assert find_word("The Doors of Durin, Lord of Moria. Speak friend and enter. "
                     "I Narvi made them. Celebrimbor of Hollin drew these signs") == "durin", "Durin"
    assert find_word("Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy."
                     " According to a researcher at Cambridge University.") == "according", "Research"
    assert find_word("One, two, two, three, three, three.") == "three", "Repeating"