#include <fstream>

#include <iostream>

#include <vector>

#include <stack>

#define nmax 100005



using namespace std;



//ifstream fin("date.in");

ifstream fin("ctc.in");

ofstream fout("ctc.out");



vector <int> G1[nmax], G2[nmax], sol[nmax];

int n, m, x, y, viz[nmax], nr_el;

stack <int> S;



void read(){

    fin >> n >> m;

    for(int i = 1; i <= m; ++i){

        fin >> x >> y;

        G1[x].push_back(y);

        G2[y].push_back(x);

    }

}



void DFS1(int nod){

    viz[nod] = 1;

    for(int i = 0; i < G1[nod].size(); ++i)

        if(!viz[G1[nod][i]])

            DFS1(G1[nod][i]);

    S.push(nod);

}



void DFS2(int nod){

    viz[nod] = 2;

    sol[nr_el].push_back(nod);

    for(int i = 0; i < G2[nod].size(); ++i)

        if(viz[G2[nod][i]] == 1)

            DFS2(G2[nod][i]);

}



void kosaraju(){

    for(int i = 1; i <= n; ++i)

        if(viz[i] == 0)

            DFS1(i);

    while(!S.empty()){

        if(viz[S.top()] == 1){

            nr_el++;

            DFS2(S.top());

        }

        S.pop();

    }

    fout << nr_el << '\n';

    for(int i = 1; i <= nr_el; ++i){

        for(int j = 0; j < sol[i].size(); ++j)

            fout << sol[i][j] << " ";

        fout << '\n';

    }

}



int main(){

    read();

    kosaraju();

    fin.close();

    fout.close();

    return 0;

}