#include <fstream>
#include <vector>

#define NMAX 100002

using namespace std;

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

int n, m, nrctc;
vector<int> G[NMAX];
vector<int> GT[NMAX]; //graful transpus

vector<int> CTC[NMAX]; //voi retine componentele conexe (reprezentate efectiv)
bool viz[NMAX];
int postordine[NMAX], h;

void citire();
void dfs(int x);
void dfst(int x);
void afisare();

int main()
{
    int i;
    citire();
    for(i = 1; i <= n; i++)
        if(!viz[i])
        {
           dfs(i);
        }
    //voi refolosi vectorul viz astfel incat cele marcate cu 1 sunt defapt cele nevizitate
    //astfel, nu mai trebuie sa resetez
    for(i = n; i > 0; i--)
        if(viz[postordine[i]])
        {
            nrctc++; //creste numarul de componente tari conexe
            dfst(postordine[i]);
        }
    afisare();
    return 0;
}

void citire()
{
 int i, x, y;
 fin>>n>>m;
 for(i = 1; i <= m; i++)
 {
     fin>>x>>y;
     G[x].push_back(y);
     GT[y].push_back(x);
 }
}

void dfs(int x)
{
 int i;
 viz[x] = 1;
 for(i = 0; i < G[x].size(); i++)
    if(!viz[G[x][i]])
      dfs(G[x][i]);
 postordine[++h] = x;
}

void dfst(int x)
{
 int i;
 viz[x] = 0;
 CTC[nrctc].push_back(x);
 for(i = 0; i < GT[x].size(); i++)
    if(viz[GT[x][i]])
      dfst(GT[x][i]);
}

void afisare()
{
 int i, j;
 fout<<nrctc<<'\n';
 for(i = 1; i <= n; i++)
    if(CTC[i].size())
    {
       for(j = 0; j < CTC[i].size(); j++)
          fout<<CTC[i][j]<<' ';
       fout<<'\n';
    }
}