class brute_force {
public:
    explicit brute_force(graph g) : _g(std::move(g)) {};
    void fill_set();

private:
    graph _g;
    std::unordered_set<graph, graph_hash> all_subgraphs;

    void impl_fill(graph const& g);
};
void brute_force::impl_fill(graph const& g) {
    if(all_subgraphs.find(g) == all_subgraphs.end()) {
        if(g.is_reachable(_s, _d)) {
            all_subgraphs.insert(g);
            for(size_t i = 0; i < g.num_edges(); ++i) {
                graph tmp = g.erase_edge(i);
                impl_fill(tmp);
            }
        }
    }
}

void brute_force::fill_set() {
    impl_fill(_g);
}

class graph {
public:
    using byte = unsigned char;
    using edge_type = std::vector<std::pair<byte, byte>>;

    graph() = default;
    graph(graph const& other) = default;
    graph(edge_type edges, byte n) : edges(std::move(edges)), n(n) {};

    bool is_reachable(byte s, byte d) const;
    graph erase_edge(size_t const& i) const;

    friend bool operator==(graph const& lhs, graph const& rhs);

    size_t num_edges() const;
private:
    edge_type edges; //список ребёр
    byte n = 0; //число вершин
};

graph graph::erase_edge(size_t const& i) const {
    graph res(*this);
    res.edges.erase(edges.begin()+i);
    return res;
}
size_t graph::num_edges() const {
    return edges.size();
}