#include <optional>
#include <span>
#include <vector>
struct TarjanEcc {
    std::vector<std::vector<std::pair<size_t, size_t>>> adj;
    std::vector<size_t> dfn, low;
    std::vector<bool> is_bridge;
    std::vector<std::vector<size_t>> eccs;
    size_t dfs_clock;
    TarjanEcc(std::span<std::pair<size_t, size_t>> edges, size_t n)
        : adj(n), dfn(n), low(n), is_bridge(edges.size(), false), eccs(), dfs_clock(0) {
        for (size_t i = 0; i < edges.size(); ++i) {
            auto [u, v] = edges[i];
            adj[u].emplace_back(v, i);
            adj[v].emplace_back(u, i);
        }
        for (size_t u = 0; u < n; ++u) {
            if (!dfn[u]) {
                find_bridges(u, std::nullopt);
            }
        }
        std::vector<bool> visited(n);
        for (size_t u = 0; u < n; ++u) {
            if (!visited[u]) {
                std::vector<size_t> q;
                q.emplace_back(u);
                visited[u] = true;
                for (size_t ptr = 0; ptr < q.size(); ++ptr) {
                    auto v = q[ptr];
                    for (auto [w, id]: adj[v]) {
                        if (!is_bridge[id] && !visited[w]) {
                            visited[w] = true;
                            q.push_back(w);
                        }
                    }
                }
                eccs.emplace_back(std::move(q));
            }
        }
    }

private:
    void find_bridges(size_t u, std::optional<size_t> prev) {
        dfn[u] = low[u] = ++dfs_clock;
        for (auto [v, id]: adj[u]) {
            if (prev == id) {
                continue;
            }
            if (!dfn[v]) {
                find_bridges(v, id);
                low[u] = std::min(low[u], low[v]);
                is_bridge[id] = dfn[u] < low[v];
            } else {
                low[u] = std::min(low[u], dfn[v]);
            }
        }
    }
};

int main() {
    int n, m;
    scanf("%d %d", &n, &m);
    std::vector<std::pair<size_t, size_t>> edges(m);
    for (auto &[u, v]: edges) {
        scanf("%zu %zu", &u, &v);
    }
    TarjanEcc ecc(edges, n + 1);
    for (size_t i = 0; i < m; ++i) {
        if (ecc.is_bridge[i]) {
            printf("%lu %lu\n", edges[i].first, edges[i].second);
        }
    }
    return 0;
}

answer.code: In function ‘int main()’:
answer.code:62:5: error: ‘scanf’ was not declared in this scope
   62 |     scanf("%d %d", &n, &m);
      |     ^~~~~
answer.code:70:13: error: ‘printf’ was not declared in this scope
   70 |             printf("%lu %lu\n", edges[i].first, edges[i].second);
      |             ^~~~~~
answer.code:4:1: note: ‘printf’ is defined in header ‘<cstdio>’; did you forget to ‘#include <cstdio>’?
    3 | #include <vector>
  +++ |+#include <cstdio>
    4 | struct TarjanEcc {