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

using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

class Graph{

private:
    vector< vector<int> > listaAdiacenta;
    vector< vector<int> > listaAdiacentaT;
    vector<int> vizitat;
    vector<int> vizitatT;
    stack <int> Stiva;
    vector < vector<int> > componente;
    int n;
public:
    Graph(int n1) : n(n1){
        this->listaAdiacenta.resize(n1 + 1);
        this->listaAdiacentaT.resize(n1 + 1);
        this->vizitat.resize(n1 + 1);
        this->vizitatT.resize(n1 + 1);
        this->componente.resize(n1 + 1);

        for(int i = 0;i<=n1;++i)vizitat[i] = vizitatT[i] = 0;
    };

    void adaugMuchie(int deLa, int la){
        this->listaAdiacenta[deLa].push_back(la);
    }

    void adaugMuchieT(int deLa, int la){
        this->listaAdiacentaT[deLa].push_back(la);
    }

    void dfs(int varf){
        vizitat[varf] = true;
        for (int p: listaAdiacenta[varf]) {
            if(!vizitat[p]){
                dfs(p);
            }
        }
    }

    void dfs1(int varf){
        vizitat[varf] = 1;
        for (int p: listaAdiacenta[varf]) {
            if(!vizitat[p]){
                dfs1(p);
            }
        }
        Stiva.push(varf);
    }

    void dfs2(int varf, int contorComp){
        vizitatT[varf] = 1;
        componente[contorComp].push_back(varf);
        for (int p: listaAdiacentaT[varf]) {
            if(!vizitatT[p]){
                dfs2(p, contorComp);
            }
        }
    }

    int nrComponenteConexe(){

        int contor = 0;
        for(int i = 1;i<=n;++i){
            if(!vizitat[i]){
                ++contor;
                dfs(i);
            }
        }

        return contor;

    }

    void print(){
        for (int i = 1; i <= n; i++)
        {
            // print the current vertex number
            cout << i << " ---> ";

            // print all neighboring vertices of a vertex `i`
            for (int v: listaAdiacenta[i]) {
                cout << v << " ";
            }
            cout << endl;
        }
    }

    void bfs(int startNo){

        int prim, ultim, i;
        queue <int> q;
        q.push(startNo);

        vizitat[startNo] = 1;

        while (!q.empty()){
            int nodAcutal = q.front();
            q.pop();
            for (int p: listaAdiacenta[nodAcutal]) {

                if(vizitat[p] == 0){
                    vizitat[p] = vizitat[nodAcutal] + 1;
                    q.push(p);
                }

            }
        }
    }

    void afisareVizitat(){
        for(int i = 1;i<=n;++i)fout<<vizitat[i] - 1<<" ";
    }

    void componenteTare(){


        for(int i = 1;i<=n;++i){
            if(!vizitat[i]){
                dfs1(i);
            }
        }

        int contorComp = 0;
        while(!Stiva.empty()){

            int varf = Stiva.top();
            Stiva.pop(); /// nu l mai folosim
            if(!vizitatT[varf]){
                contorComp++;
                dfs2(varf, contorComp);
            }
        }

        fout<<contorComp<<endl;
        for(int i = 1;i<=contorComp;++i){
            int lungime = componente[i].size();
            for (int j = 0;j<lungime;++j){
                fout<<componente[i][j]<<" ";
            }
            fout<<endl;
        }


    }

};

int main()
{
    int n, m;
    fin>>n>>m;
    Graph g(n);
    for(int i = 1;i<=m;++i){
        int a, b;
        fin>>a>>b;
        g.adaugMuchie(a, b);
        g.adaugMuchieT(b, a);
    }
    g.componenteTare();
    return 0;
}