#include <bits/stdc++.h>
#include<fstream>
#include<vector>
#include<map>
#include<queue>
#include<deque>
#include<algorithm>
std::ifstream f("ctc.in");
std::ofstream fg("ctc.out");
int n, m, a, b;

class graf{
public:
    int n, m;

    graf(int n, int m);

    std::vector<std::vector<int> > lista;
    std::vector<int> viz;
    std::vector<int> low;
    std::vector<int> membru;
    std::deque<int> st;
    std::vector< std::vector<int> > componente;

    int nr_comp_conex = 0;

    void new_lista( int nod1, int nod2);
    void dfs(int nod);
    void comp_conex();

};

graf::graf(int n, int m) {
    this->n = n;
    this->m = m;

    std::vector<int> v;
    for(auto i = 0 ; i<=n ; i++){
        viz.push_back(-1);
        low.push_back(-1);
        membru.push_back(0);
        lista.push_back(v);
    }
}

void graf::new_lista(int nod1, int nod2){
    lista[nod1].push_back(nod2);
    //lista[nod2].push_back(nod1);
}

void graf::dfs(int nod){
    static int cnt = 0;
    viz[nod] = ++cnt;
    low[nod] = cnt;
    st.push_back(nod);
    membru[nod] = 1;

    for( auto i = lista[nod].begin(); i != lista[nod].end(); i++) {
        if (viz[*i] == -1) {
            dfs(*i);
            low[nod] = fmin(low[nod], low[*i]);
        } else if (membru[*i] == 1) {
            low[nod] = fmin(low[nod], viz[*i]);
        }
    }

    int aux = 0;
    if(low[nod] == viz[nod]){

        std::vector<int>v;
        componente.push_back(v);

        while(st.back() != nod){
            aux = st.back();
            //std::cout<< aux<<" ";

            componente[nr_comp_conex].push_back(aux);
            membru[aux] = 0;
            st.pop_back();
        }

        aux = st.back();
        //std::cout<< aux<<"\n ";
        componente[nr_comp_conex].push_back(aux);
        membru[aux] = 0;
        st.pop_back();

        ++nr_comp_conex;
    }

}

void graf::comp_conex(){
    for(int i = 0 ; i< n ; i++){
        if(viz[i] == -1) dfs(i);
    }

    fg<<nr_comp_conex<<"\n";

    for(int i= 0 ; i<nr_comp_conex ; i++){
        for(auto j= componente[i].begin(); j!=componente[i].end(); j++)
            fg<<*j + 1<<" ";
        fg<<"\n";
    }

    /*std::cout<<"\n";
    for(int i=0 ; i<n ; i++)
        std::cout<<viz[i]<<" ";

    std::cout<<"\n";
    for(int i=0 ; i<n ; i++)
        std::cout<<low[i]<<" ";*/

}


int main() {
    f>>n>>m;

    graf g(n, m);
    for(int i=0 ; i<m ; i++){
        f>>a>>b;
        g.new_lista(a-1,b-1);
    }

    g.comp_conex();
    return 0;
}