TNode* Solve() {
    std::vector<TNode*> current;
    for (auto node : GetNodes())
        current.push_back(node);
    for (; current.size() > 1;) {
        std::vector<TNode*> next;
        for (size_t i = 0; i < current.size();) {
            size_t j = i + 1;
            for (; j < current.size(); ++j) {
                if (hasEdge(current[i], current[j]))
                    break;
            }
            if (j == current.size()) {
                next.push_back(current[i]);
                ++i;
            } else {
                i = j;
            }
        }
        current.swap(next);
    }
    return current.front();
}