#include <iostream>
#include <fstream>
#define Nmax  100301
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
int n,m;
struct nod
{
    int info;
    nod *urm;
};
nod *gf[Nmax];//graful orientat
nod *gft[Nmax];//graful orientat transpus
nod *sol[Nmax];//cate o componenta tare conexa in fiecare lista
int nrCTC;//numarul de componente tare conexe
int vizT[Nmax],viz[Nmax];
int timpi_finali[Nmax],nr;
void ADD (nod *&prim,int x)
{
    nod *q=new nod;
    q->info=x;
    q->urm=prim;
    prim=q;
}
void Citire()
{
    int i;
    int x,y;
    fin>>n>>m;
    for (i=1; i<=m; i++)
    {
        fin>>x>>y;
        ADD(gf[x],y);
        ADD(gft[y],x);
    }

}
void DFS (int x)
{
    viz[x]=1;
    nod *p;
    for (p=gf[x]; p!=NULL; p=p->urm)
        if (viz[p->info]==0)DFS(p->info);
        nr++;timpi_finali[nr]=x;
}
void DFST (int x)
{
    vizT[x]=1;
    nod *p;
    ADD(sol[nrCTC],x);
    for (p=gft[x]; p!=NULL; p=p->urm)
        if (vizT[p->info]==0)DFST(p->info);

}

void Rezolva ()
{
    int i,ok=1,viz1[]= {0};
    nod*p;
    for (i=1; i<=n; i++) //Prima parcurgere
        if (viz[i]==0)
            DFS(i);
    for (i=nr; i>=1; i--) //A 2-a parcurgere
        if (vizT[timpi_finali[i]]==0)
        {
            nrCTC++;
            DFST(timpi_finali[i]);
        }

    fout<<nrCTC<<"\n";
    for (i=1; i<=nrCTC; i++)
    {
        for (p=sol[i]; p!=NULL; p=p->urm)
            fout<<p->info<<" ";
        fout<<"\n";
    }


}
int main()
{
    int i;
    nod *p;
    Citire();

    Rezolva();


    return 0;
}