Stats ExploreKeyWords(const KeyWords &key_words, istream &input) {
    vector<future<Stats>> futures;
    for (string line; getline(input, line);) {
        futures.push_back(async([key_words, line] {
            const auto words = Split(line);
            Stats stat;
            for (const auto &key: key_words) {
                stat.word_frequences[key] += std::count(std::execution::par, words.begin(), words.end(), key);
            }
            return stat;
        }));
    }
    Stats result;
    std::for_each(std::execution::par, futures.begin(), futures.end(), [&result](auto &f) { result += f.get(); });
    return result;
}