#include <bits/stdc++.h>

using namespace std;

ifstream fin("biconex.in");
ofstream fout("biconex.out");
class Graph {

private:

    //Variabile private

    int vertices;
    int edges;
    bool oriented;
    vector<int> *adjacency_list;

    //To compute:
    vector<list<int>> biconnected_components;
    vector<vector<int>> strongly_connected_components;
    vector<int> topological;

    //Functii private

    void BFS(int starting_vertex, int *distances);

    void DFS(int vertex,int* visited);

    void BCC(int vertex,vector<int>& parent, stack<int>& vertices_stack, vector<int>& discovery_time,vector<int>& lowest_reachable,int& timer);

    void SCC(int vertex,vector<int>& discovery_time,vector<int>& lowest_reachable, stack<int> &vertices_stack, vector<bool> &on_stack,int& timer);

    void TOPOLOGICAL_SORT(int vertex,vector<bool>& visited);

public:

    Graph(int vertices = 0, int edges = 0, bool oriented = false);

    ~Graph();

    void infoarena_graph();

    void show_my_graph();

    void solve_distances(int starting_vertex);

    void solve_connected_components();

    void solve_biconnected();

    void solve_strongly_connected();

    void solve_topological();

};

int main() {
    int N,M;
    fin>>N>>M;
    Graph g(N,M, false);
    g.infoarena_graph();
    g.solve_biconnected();
}

#pragma region Initialization
Graph::Graph(int vertices, int edges, bool oriented) : vertices(vertices), edges(edges), oriented(oriented) {
    adjacency_list = new vector<int>[vertices + 1];
}

Graph::~Graph() {
    delete[] adjacency_list;
}

void Graph::infoarena_graph() {
    int x, y;
    if (oriented) {
        for (int i = 1; i <= edges; i++) {
            fin >> x >> y;
            adjacency_list[x].push_back(y);
        }
    } else {
        for (int i = 1; i <= edges; i++) {
            fin>>x>>y;
            adjacency_list[x].push_back(y);
            adjacency_list[y].push_back(x);
        }
    }
}

void Graph::show_my_graph() {
    for(int i = 1;i<vertices+1;i++){
        cout<<i<<"=>";

        for(int j : adjacency_list[i]){
            cout<<j<<' ';
        }
        cout<<'\n';
    }
}

#pragma endregion

//Algorithm implementations
#pragma region Algorithms

void Graph::BFS(int starting_vertex, int *distances) {

    int* visited = (int*) calloc(vertices+1,sizeof (int));
    queue<int> que;
    que.push(starting_vertex);

    distances[starting_vertex] = 1;
    visited[starting_vertex] = 1;

    while (!que.empty()) {
        int current_node = que.front();
        que.pop();

        for (auto neighbor : adjacency_list[current_node]) {
            if (!visited[neighbor]) {
                que.push(neighbor);
                visited[neighbor] = 1;
                distances[neighbor] = distances[current_node] + 1;
            }
        }
    }

    free(visited);
}

void Graph::DFS(int vertex, int *visited) {

    visited[vertex] = 1;

    for(auto neighbor : adjacency_list[vertex])
        if(!visited[neighbor])
            DFS(neighbor,visited);
}

void Graph::BCC(int vertex,vector<int>& parent, stack<int>& vertices_stack,vector<int>& discovery_time,vector<int>& lowest_reachable,int& timer){

    // consider lowest reachable value as being a better path from a node to another
    // for example if we want to reach a certain point and we have 2 neighbors with different discovery time we will chose
    // the one with the less value because we want to reach faster that certain point

    // increment the discovery time of the vertex you are visiting
    // this is the only information you posses at the moment
    discovery_time[vertex] = lowest_reachable[vertex] = ++timer;

    for(int neighbor : adjacency_list[vertex]){

        vertices_stack.push(vertex);

        if(neighbor != parent[vertex]) {

            //now for each neighbor you are checking in adjacency list you are pushing on stack the vertex you are currently visiting
            //assuming it is an articulation point

            //if the neighbor you are checking has not been visited yet you will visit him next via DFS
            if (parent[neighbor] == -1) {

                parent[neighbor] = vertex; //set the parent of neighbor to be te current node
                BCC(neighbor, parent, vertices_stack, discovery_time,lowest_reachable, timer); //DFS

                //After you reach a point when DFS cant visit unvisited nodes you get back and update the values of your vertex lowest_reachable point
                //with the values of the neighbor you currently visited and set it to the min value between both of them
                lowest_reachable[vertex] = min(lowest_reachable[neighbor],
                                               lowest_reachable[vertex]);
                //You do this operation until you are in a vertex which has its discovery time less than or equal to the lowest reachable
                //value of the neighbor you currently visited


                //if you manage to find such a vertex, that means it is an articulation point, and all the vertices
                //you pushed into the stack by now are part of a biconnected component

                if (discovery_time[vertex] <= lowest_reachable[neighbor]) {
                    list<int> component;
                    vector<bool> pushed(vertices+1,false);
                    component.push_back(vertex);
                    pushed[vertex] = true;
                    int temp = vertices_stack.top();

                    while(temp!=vertex){
                        if(!pushed[temp]){
                            component.push_back(temp);
                            pushed[temp] = true;
                        }
                        vertices_stack.pop();
                        temp = vertices_stack.top();
                    }
                    biconnected_components.push_back(component);
                }
            }

                //if the neighbor you are visiting has been actually visited, we need to check if it's discovery time is less then our lowest reachable value
                //if so, that means you have a path to that node that is better than the path you are on right now, so when you
                //get back by recursion it will tell the other vertices that he found a better path and will set all other vertices' lowest_reachable value to the minimal one
                //so it will form a biconnected component
            else {
                lowest_reachable[vertex] = min(discovery_time[neighbor], lowest_reachable[vertex]);
            }
        }
    }
}


void Graph::SCC(int vertex, vector<int> &discovery_time, vector<int> &lowest_reachable, stack<int> &vertices_stack, vector<bool> &on_stack, int &timer) {

    discovery_time[vertex] = lowest_reachable[vertex] = ++timer;

    vertices_stack.push(vertex);

    on_stack[vertex] = true;

    for(auto neighbor : adjacency_list[vertex]){

        if(discovery_time[neighbor] == -1){
            SCC(neighbor,discovery_time,lowest_reachable,vertices_stack,on_stack,timer);

            lowest_reachable[vertex] = min(lowest_reachable[vertex],lowest_reachable[neighbor]);
        }

        else if(on_stack[neighbor]){
            lowest_reachable[vertex] = min(lowest_reachable[vertex],discovery_time[neighbor]);
        }
    }

    if(lowest_reachable[vertex] == discovery_time[vertex]){
        vector<int> component;

        int temp;
        do{
            temp = vertices_stack.top();
            vertices_stack.pop();
            on_stack[temp] = false;
            component.push_back(temp);
        }while(temp!=vertex);

        strongly_connected_components.push_back(component);
    }
}

void Graph::TOPOLOGICAL_SORT(int vertex, vector<bool> &visited) {

    visited[vertex] = true;

    for(int neighbor : adjacency_list[vertex]){
        if(!visited[neighbor])
            TOPOLOGICAL_SORT(neighbor,visited);
    }

    topological.push_back(vertex);
}

#pragma endregion


//infoarena solutions
#pragma region Solutions

//Minimal distances BFS problem
void Graph::solve_distances(int starting_vertex) {
    int *distances = (int*)calloc(vertices+1,sizeof (int));

    BFS(starting_vertex,distances);

    for(int i = 1;i<vertices+1;i++)
        fout<<distances[i] - 1<<' ';

    free(distances);
}

//Connected compontents DFS problem
void Graph::solve_connected_components() {

    int counter = 0;
    int* visited = (int*)calloc(vertices+1,sizeof (int));

    for(int i = 1;i<vertices + 1;i++)
        if(!visited[i]){
            DFS(i,visited);
            counter++;
        }

    fout<<counter;
    free(visited);
}

void Graph::solve_biconnected() {

    //initialize the stuff you will work with
    stack<int> vertices_stack;
    vector<int> parent(vertices+1,-1);
    vector<int> discovery_time(vertices+1,-1);
    vector<int> lowest_reachable(vertices+1,-1);

    //global timer for discovery time and lowest reachable value
    int timer = 0;

    parent[1] = 1;
    BCC(1,parent,vertices_stack,discovery_time,lowest_reachable,timer);

    list<int>::iterator it;
    fout<<biconnected_components.size()<<'\n';
    for(auto components : biconnected_components){
        for (it = components.begin();it!=components.end();it++)
            fout<<*it<<' ';
        fout<<'\n';
    }
}

void Graph::solve_strongly_connected(){

    vector<int> discovery_time(vertices+1,-1);
    vector<int> lowest_reachable(vertices+1,-1);
    vector<bool> on_stack(vertices+1,false);
    stack<int> vertices_stack;

    int timer = 0;

    for(int i = 1;i<vertices+1;i++){
        if(discovery_time[i]==-1)
            SCC(i,discovery_time,lowest_reachable,vertices_stack,on_stack,timer);
    }

    fout<<strongly_connected_components.size()<<'\n';

    for(auto component : strongly_connected_components){
        for(int i : component)
            fout<<i<<' ';
        fout<<'\n';
    }
}

void Graph::solve_topological() {

    vector<bool> visited(vertices+1,false);

    for(int i = 1;i<vertices+1;i++) {
        if (!visited[i])
            TOPOLOGICAL_SORT(i, visited);
    }

    for(int i = topological.size()-1;i>-1;i--){
        fout<<topological[i]<<' ';
    }
}

#pragma endregion