#include <fstream>
#define NMAX 100004
#include <vector>
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");
int n;
///graful G repr prin liste de adiacenta
vector <int> G[NMAX];
///graful transpus GT repr prin liste de adiacenta
vector <int> GT[NMAX];
bool viz[NMAX];
int nr;///nr de componente-tare conexe
vector <int> ctc[NMAX];
int postordine[NMAX];
void citire();
void afisare();
void DFS(int x);
void DFST(int x);
int main()
{int i;
    citire();
    ///parcurg DFS graful G retinand varfurile in psotordine
    for (i=1; i<=n; i++)
        if (viz[i]==0)///nu e vizitat
             DFS(i);
    ///parcurg vectorul postordine de la dr la st si fac DFS dar nu in graful initial ci in graful transpus
    for (i=n; i>0; i--)
        if (viz[postordine[i]]==1)///acest vf este nevizitat in GT
            {
             nr++;
             DFST(postordine[i]);
            }
    afisare();
    return 0;
}

void citire()
{
    int i, x, y, m;
    fin>>n>>m;
    for (i=0; i<m; i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS(int x)
{int i,poz;
    viz[x]=1;
    ///parcurg lista de adiacemta a lui x
    for (i=0; i<G[x].size(); i++)
        if (viz[G[x][i]]==0)
            DFS(G[x][i]);
    postordine[++poz]=x;
}

void DFST(int x)
{int i;
    viz[x]=0;
    ///parcurg lista de adiacemta a lui x
    ///retin acest vf in comp conexa curenta care are numarul nr
    ctc[nr].push_back(x);
    for (i=0; i<GT[x].size(); i++)
        if (viz[GT[x][i]]==1)///nevizitat
            DFST(GT[x][i]);
}

void afisare()
{
    int i, j;
    fout<<nr<<endl;
    for (i=1; i<=nr; i++)
        {
           for (j=0; j<ctc[i].size(); j++)
              fout<<ctc[i][j]<<' ';
           fout<<endl;
        }
}