#include <iostream>
#include <fstream>
#include <vector>
#include <stack>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n, m, st, dr, nr = 0;
vector <vector<int>> listaAd, listaTr, rez;
vector <int> vizitat, vizitatTr;
stack <int> stiva;
 
void dfs1(int nod)
{
    vizitat[nod] = 1;
    for (int i = 0; i < listaAd[nod].size(); i++)
    {
        int nod_curent = listaAd[nod][i];
        if (vizitat[nod_curent] == 0)
            dfs1(nod_curent);
    }
   stiva.push(nod);
}
 
void dfs2(int nod, vector<int> &vector_aux)
{
    vector_aux.push_back(nod);
    vizitatTr[nod] = 1;
    for (int i = 0; i < listaTr[nod].size(); i++)
    {
        int nod_curent = listaTr[nod][i];
        if (vizitatTr[nod_curent] == 0)
            dfs2(nod_curent, vector_aux);
    }
}
 
int main()
{
    fin >> n >> m;
    rez = vector <vector<int>> (n + 1);
    listaTr = vector <vector<int>> (n + 1);
    listaAd = vector <vector<int>> (n + 1);
    vizitat = vector <int> (n + 1, 0);
    vizitatTr = vector <int> (n + 1, 0);
    for (int i = 1; i <= m; i++)
    {
        fin >> st >> dr;
        listaAd[st].push_back(dr);
        listaTr[dr].push_back(st);
    }
    int nr = 0;
    for (int i = 1; i <= n; i++)
        if (vizitat[i] == 0)
            dfs1(i);
    while (stiva.empty() == 0)
    {
       int v = stiva.top();
       stiva.pop();
       if (vizitatTr[v] == 0)
       {
          vector <int> vector_aux;
          dfs2(v, vector_aux);
          rez.push_back(vector_aux);
          nr++;
       }
    }
    fout << nr;
    for (int i = 0; i < rez.size(); i++)
    {
       for (int j = 0; j < rez[i].size(); j++)
           fout << rez[i][j] << " ";
       fout << "\n";
    }
    fin.close();
    fout.close();
    return 0;
}