#include <iostream>
#include <vector>
#include <queue>
#include <stack>
#include <algorithm>
#include <fstream>

using namespace std;

ifstream in("biconex.in");
ofstream out("biconex.out");

class Graf
{
    int tip;
    int nr_noduri;
    int nr_muchii;
    vector <vector <int>> lista_vecini;

public:
    Graf() {
        tip = 0;
        nr_noduri = 0;
        nr_muchii = 0;
    }
    Graf(int tip, int nr_noduri, int nr_muchii, vector <vector<int>> lista_vecini) {
        this->tip = tip;
        this->nr_noduri = nr_noduri;
        this->nr_muchii = nr_muchii;
        this->lista_vecini.resize(nr_noduri + 1);
        for (int i = 1; i <= nr_noduri; i++)
            for (int j = 0; j < lista_vecini[i].size(); j++)
                this->lista_vecini[i].push_back(lista_vecini[i][j]);
    }
    ~Graf() { }

    friend istream& operator>>(istream& in, Graf& g);
    friend ostream& operator<<(ostream& out, const Graf& g);

    void BFS() {
        cout << "\nIntroduceti nodul de start: ";
        int start;
        cin >> start;

        queue <int> bfs_tree;
        vector <int> viz;
        for (int i = 0; i <= this->nr_noduri; i++)
            viz.push_back(-1);

        bfs_tree.push(start);
        viz[start] = 0;

        while (!bfs_tree.empty()) {
            int nod_curent = bfs_tree.front();
            bfs_tree.pop();

            for (int i = 0; i < lista_vecini[nod_curent].size(); i++)
                if (viz[lista_vecini[nod_curent][i]] == -1) {
                    viz[lista_vecini[nod_curent][i]] = viz[nod_curent] + 1;
                    bfs_tree.push(lista_vecini[nod_curent][i]);
                }
        }

        cout << "\nVectorul distantelor: ";
        for (int i = 1; i <= this->nr_noduri; i++)
            cout << viz[i] << " ";
    }
    void DFS(int start, vector <int> &viz) {
        stack <int> dfs_tree;

        dfs_tree.push(start);
        viz[start] = 1;

        while (!dfs_tree.empty()) {
            int nod_curent = dfs_tree.top();
            int vecin = 0;
            for (int i = 0; i < lista_vecini[nod_curent].size(); i++)
                if (viz[lista_vecini[nod_curent][i]] == 0) {
                    vecin = lista_vecini[nod_curent][i];
                    break;
                }
            if (vecin == 0)
                dfs_tree.pop();
            else {
                dfs_tree.push(vecin);
                viz[vecin] = 1;
            }
        }

    }
    void comp_conexe() {
        vector <int> viz;
        for (int i = 0; i <= this->nr_noduri; i++)
            viz.push_back(0);

        int nr_comp = 0;

        for(int i=1; i<=this->nr_noduri; i++)
            if(viz[i] == 0) {
                DFS(i, viz);
                nr_comp++;
            }

        cout << "\nNumar de componente conexe: " << nr_comp << " ";
    }
    void havel_hakimi() {
        int seq_len;
        vector <int> seq;
        int sum = 0;
        int ok = 1;
        cin >> seq_len;
        for (int i = 0; i < seq_len; i++) {
            int aux;
            cin >> aux;
            seq.push_back(aux);
            sum = sum + aux;
            if (aux > seq_len - 1)
                ok = 0;
        }
        if (sum % 2 != 0 || ok == 0)
            cout << "Nu";
        else {
            sort(seq.begin(), seq.end(), greater<int>());
            while (seq[0] != 0) {
                int nod_curent = seq[0];
                seq.erase(seq.begin());
                for (int i = 0; i < nod_curent; i++) {
                    seq[i]--;
                    if (seq[i] < 0) {
                        cout << "Nu";
                        ok = 0;
                        break;
                    }
                }
                sort(seq.begin(), seq.end(), greater<int>());
            }
            if (ok == 1)
                cout << "Da";
        }

    }
    void dfs_muchiiIntoarcere(int i, vector <int>& viz, vector <int>& niv, vector<int>& niv_min, vector <vector<int>>& solutie) {
        viz[i] = 1;
        niv_min[i] = niv[i];
        for (int j = 0; j < lista_vecini[i].size(); j++)
            if (viz[lista_vecini[i][j]] == 0) {
                niv[lista_vecini[i][j]] = niv[i] + 1;
                dfs_muchiiIntoarcere(lista_vecini[i][j], viz, niv, niv_min, solutie);
                niv_min[i] = min(niv_min[i], niv_min[lista_vecini[i][j]]);
                if (niv_min[lista_vecini[i][j]] > niv[i]) {
                    solutie.push_back({ i,lista_vecini[i][j] });
                }
            }
            else {
                if (niv[lista_vecini[i][j]] < niv[i] - 1)
                    niv_min[i] = min(niv_min[i], niv[lista_vecini[i][j]]);
            }
    }
    void criticalConnections() {
        vector <vector<int>> solutie;
        vector <int> viz;
        vector <int> niv;
        vector <int> niv_min;

        for (int i = 0; i <= nr_noduri; i++)
            viz.push_back(0);
        niv.resize(nr_noduri + 1);
        niv_min.resize(nr_noduri + 1);
        niv[1] = 1;
        dfs_muchiiIntoarcere(1, viz, niv, niv_min, solutie);

        for (int i = 0; i < solutie.size(); i++)
            cout << solutie[i][0] << " " << solutie[i][1] << "\n";
    }
    void tare_conex(int i, vector <int> &onStack, vector <int> &viz, vector <int> &niv_min, int &index, stack <int> &s, int &nr, vector <vector<int>> &solutie) {
        viz[i] = index;
        niv_min[i] = index;
        index++;
        s.push(i);
        onStack[i] = 1;

        for (int j = 0; j < lista_vecini[i].size(); j++)
            if (viz[lista_vecini[i][j]] == 0) {
                tare_conex(lista_vecini[i][j], onStack, viz, niv_min, index, s, nr, solutie);
                niv_min[i] = min(niv_min[i], niv_min[lista_vecini[i][j]]);
            }
            else if (onStack[lista_vecini[i][j]] == 1)
                niv_min[i] = min(niv_min[i], viz[lista_vecini[i][j]]);

        int j = 0;
        if (niv_min[i] == viz[i]) {
            nr++;
            while (s.top() != i) {
                j = s.top();
                solutie[nr].push_back(j);
                onStack[j] = 0;
                s.pop();
            }
            j = s.top();
            solutie[nr].push_back(j);
            onStack[j] = 0;
            s.pop();
        }
    }
    void tarjan() {
        vector <int> onStack;
        vector <int> viz;
        vector <int> niv_min;
        vector <vector<int>> solutie;
        int nr = 0;
        niv_min.resize(nr_noduri + 1);
        solutie.resize(nr_noduri + 1);
        for (int i = 0; i <= nr_noduri; i++) {
            onStack.push_back(0);
            viz.push_back(0);
        }

        int index = 1;
        stack <int> s;
        for (int i = 1; i <= nr_noduri; i++)
            if (viz[i] == 0)
                tare_conex(i, onStack, viz, niv_min, index, s, nr, solutie);


        cout << nr << "\n";
        for (int i = 1; i <= nr; i++) {
            for (int j = 0; j < solutie[i].size(); j++)
                cout << solutie[i][j] << " ";
            cout << "\n";
        }
    }
    void dfs_sortare(int nod_curent, vector <int> &viz, vector <int> &solutie) {
        viz[nod_curent] = 1;
        for (int i = 0; i < lista_vecini[nod_curent].size(); i++)
            if (viz[lista_vecini[nod_curent][i]] == 0)
                dfs_sortare(lista_vecini[nod_curent][i], viz, solutie);
        solutie.push_back(nod_curent);
    }
    void sortare_top() {
        vector <int> solutie;
        vector <int> viz;
        for (int i = 0; i <= nr_noduri; i++)
            viz.push_back(0);

        for (int i = 1; i <= nr_noduri; i++)
            if (viz[i] == 0)
                dfs_sortare(i, viz, solutie);

        for (int i = solutie.size() - 1; i >= 0; i--)
            cout << solutie[i] << " ";
        cout << "\n";
    }
    void dfs_biconex(int i, int &index,vector <int>& niv, vector <int>& niv_min, vector <int> &tata, stack <pair<int, int>>& muchii, int &nr_comp, vector <vector <pair<int,int>>>& solutie) {
        niv[i] = index;
        niv_min[i] = index;
        index++;
        int nr_copii = 0;

        for (int j = 0; j < lista_vecini[i].size(); j++) {
            if (niv[lista_vecini[i][j]] == 0) {
                nr_copii++;
                tata[lista_vecini[i][j]] = i;
                muchii.push(make_pair(i, lista_vecini[i][j]));

                dfs_biconex(lista_vecini[i][j], index, niv, niv_min, tata, muchii, nr_comp, solutie);

                niv_min[i] = min(niv_min[i], niv_min[lista_vecini[i][j]]);
                if ((niv[i] == 1 && nr_copii > 1) || (niv[i] > 1 && niv_min[lista_vecini[i][j]] >= niv[i])) {
                    while (muchii.top().first != i || muchii.top().second != lista_vecini[i][j]) {
                        solutie[nr_comp].push_back(muchii.top());
                        muchii.pop();
                    }
                    solutie[nr_comp].push_back(muchii.top());
                    muchii.pop();
                    nr_comp++;
                }
            }
            else if (lista_vecini[i][j] != tata[i]) {
                niv_min[i] = min(niv_min[i], niv[lista_vecini[i][j]]);
                if (niv[lista_vecini[i][j]] < niv[i])
                    muchii.push(make_pair(i, lista_vecini[i][j]));
            }
        }
    }
    void biconex() {
        vector <int> niv;
        vector <int> niv_min;
        vector <int> tata;
        stack <pair <int, int>> muchii;
        vector <vector <pair <int, int>>> solutie;
        niv_min.resize(nr_noduri + 1);
        solutie.resize(nr_noduri);
        for (int i = 0; i <= nr_noduri; i++) {
            niv.push_back(0);
            tata.push_back(0);
        }
        int index = 0;
        int nr_comp = 0;

        for (int i = 1; i <= nr_noduri; i++)
            if (niv[i] == 0)
                dfs_biconex(i, index, niv, niv_min, tata, muchii, nr_comp, solutie);

        int ok = 0;
        while (!muchii.empty()) {
            solutie[nr_comp].push_back(muchii.top());
            muchii.pop();
            ok = 1;
        }
        if (ok == 1)
            nr_comp++;

        out << nr_comp << "\n";
        for (int i = 0; i < solutie.size(); i++) {
            vector <int> noduri;
            for (int i = 0; i <= nr_noduri; i++)
                noduri.push_back(0);
            for (int j = 0; j < solutie[i].size(); j++) {
                if (noduri[solutie[i][j].first] == 0) {
                    out << solutie[i][j].first << " ";
                    noduri[solutie[i][j].first] = 1;
                }
                if (noduri[solutie[i][j].second] == 0) {
                    out << solutie[i][j].second << " ";
                    noduri[solutie[i][j].second] = 1;
                }
            }
            out << "\n";
        }

    }
};

istream& operator>>(istream& in, Graf& g)
{
    cout << "\nIntroduceti tipul grafului (0-Neorientat 1-Orientat):";
    in >> g.tip;
    if (g.tip == 0) {
        cout << "\nIntroduceti numarul de noduri: ";
        cin >> g.nr_noduri;
        cout << "\nIntroduceti numarul de muchii: ";
        cin >> g.nr_muchii;
        cout << "\nIntroduceti lista muchiilor: ";
        g.lista_vecini.resize(g.nr_noduri + 1);
        for (int i = 0; i < g.nr_muchii; i++) {
            int x, y;
            cin >> x >> y;
            g.lista_vecini[x].push_back(y);
            g.lista_vecini[y].push_back(x);
        }
    }
    else if(g.tip == 1) {
        cout << "\nIntroduceti numarul de noduri: ";
        cin >> g.nr_noduri;
        cout << "\nIntroduceti numarul de arce: ";
        cin >> g.nr_muchii;
        cout << "\nIntroduceti lista arcelor: ";
        g.lista_vecini.resize(g.nr_noduri + 1);
        for (int i = 0; i < g.nr_muchii; i++) {
            int x, y;
            cin >> x >> y;
            g.lista_vecini[x].push_back(y);
        }
    }
    else {
        cout << "\nTip gresit";
    }

    return in;
}
ostream& operator<<(ostream& out, const Graf& g)
{
    cout << "\nTip graf: ";
    if (g.tip == 0) {
        cout << "neorientat";
        cout << "\nNumar de noduri: " << g.nr_noduri;
        cout << "\nNumar de muchii: " << g.nr_muchii;
        cout << "\nLista de vecini: ";
        for (int i = 1; i <= g.nr_noduri; i++)
        {
            for (int j = 0; j < g.lista_vecini[i].size(); j++)
                cout << g.lista_vecini[i][j] << " ";
            cout << "\n";
        }
    }
    else if (g.tip == 1) {
        cout << "orientat";
        cout << "\nNumar de noduri: " << g.nr_noduri;
        cout << "\nNumar de arce: " << g.nr_muchii;
        cout << "\nLista de vecini: ";
        for (int i = 1; i <= g.nr_noduri; i++)
        {
            for (int j = 0; j < g.lista_vecini[i].size(); j++)
                cout << g.lista_vecini[i][j] << " ";
            cout << "\n";
        }
    }

    return out;
}



int main()
{
    int n, m;
    in >> n >> m;
    vector <vector <int>> v;
    v.resize(n + 1);
    for (int i = 0; i < m; i++)
    {
        int x, y;
        in >> x >> y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    Graf G(0, n, m, v);
    G.biconex();
    return 0;
}