int nonDivisibleSubset(int k, vector<int> S) {
    std::map<int, std::set<int>> x;

    auto n = S.size();
    for (int i = 0; i < n; i++) {
        for (int j = i+1; j < n; j++) {
            if ((S[i]+S[j])%k) {
                x[std::min(S[i], S[j])].insert(std::max(S[i], S[j]));
            }
        }
    }

    std::map<int, int> tab;
    std::function<int(int)> longestPath = [&](int w) {
        if (tab.find(w) != tab.end()) return tab[w];
        if (x.find(w) == x.end()) return tab[w] = 0;

        int _max = 0;
        for (auto &it : x[w]) _max = std::max(_max, longestPath(it));

        return tab[w] = _max + 1;
    };

    int _max = 0;
    for (auto &it:x) _max = std::max(_max, longestPath(it.first));

    return _max + 1;
}