#include <fstream>
#include <vector>
#define NMAX 100002


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

int n, poz, nr;
///graful G reprezentat prin liste de adiacenta
vector<int> G[NMAX];
///graful transpus GT reprezentat prin lista de adiacenta
vector<int> GT[NMAX];
bool viz[NMAX];
int nt; ///numarul de componente tare conexe
vector<int> ctc[NMAX];
int postordine[NMAX];

void citire();
void DFS(int x);
void DFST(int x);
void afisare();

int main()
{int i;
citire();
///parcurg DFS graful G retinand varfurile in postordine
for(i=1; i<=n; i++)
    if(viz[i]==0)
        DFS(i);
///parcurg vectorul postordine de la dreapta la stanga si fac DFS dar in GT (DFST)
for(i=n; i>0; i--)
    if(viz[postordine[i]]==1) ///acest varf este nevizitat IN GT
        {nr++;
        DFST(postordine[i]);}

afisare();
    return 0;
}

void citire()
{
    int x, y, m, i;
    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;
viz[x]=1;
///parcurg lista de adiacenta 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;
///retin acest varf in componenta conexa curenta
ctc[nr].push_back(x);
///parcurg lista de adiacenta a lui x in GT
for(i=0; i<GT[x].size(); i++)
    if(viz[GT[x][i]]==1)
        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;}}