#include <cstdio>
#define NMAX 100100
using namespace std;
FILE*fout=fopen("ctc.out", "w");

char ctc[NMAX], viz[NMAX];
int postord[NMAX], lgpord;
int n, m, nr_ctc;

struct nod
        {int inf;
        struct nod *urm;
        };

typedef struct nod *Lista;
Lista A[NMAX], AT[NMAX], CTC[NMAX];

void inserare(Lista&, Lista, int);
void citire();
void DFS1(int);
void DFS2(int);
void rez();

int main()
{
    citire();
    rez();
    return 0;
}

void citire()
{
    FILE*fin=fopen("ctc.in", "r");
    fscanf(fin, "%d %d", &n, &m);
    int i, x, y;
    for (i=1; i<=m; ++i)
        {
            fscanf(fin, "%d %d", &x, &y);
            //am arc de la x la y
            inserare (A[x], NULL, y);
            //in graful transpus, am arc de la y la x
            inserare (AT[y], NULL, x);
        }
    fclose(fin);
    return;
}

void rez()
{
    int i; Lista q;
    for (i=1; i<=n; ++i)
        if (!viz[i])//nu l-am vizitat
            DFS1(i);
    //resetez vectorul viz
    for (i=1; i<=n; ++i)
        viz[i]=0;

    for (i=lgpord; i>0; --i)
        if (!ctc[postord[i]])//nu se afla in nicio componenta conexa
        {
            ++nr_ctc;
            DFS2 (postord[i]);
        }

    //afisez componentele conexe
    fprintf(fout, "%d\n", nr_ctc);
    for (i=1; i<=nr_ctc; ++i)
        {
        for (q=CTC[i]; q; q=q->urm)
            fprintf(fout, "%d ", q->inf);
        fprintf(fout, "\n");
        }
    fclose(fout);
    return;
}

void DFS1(int vf)//construiesc vectorul postordine
{
    viz[vf]=1;//l-am vizitat
    Lista q;
    for (q=A[vf]; q; q=q->urm)
        if (!viz[q->inf])
            DFS1 (q->inf);
    postord[++lgpord]=vf;
}

void DFS2 (int vf)
{
    ctc[vf]=1;
    //retin varful in componenta conexa curenta
    inserare (CTC[nr_ctc], NULL, vf);
    Lista q;
    for (q=AT[vf]; q; q=q->urm)
        if (!ctc[q->inf])
            DFS2(q->inf);
}

void inserare (Lista &prim, Lista p, int x)
{
    Lista q;
    q=new nod;
    q->inf=x;
    if (p)
    {
        q->urm=p->urm;
        p->urm=q;
    }
    else
    {
        q->urm=prim;
        prim=q;
    }
    return;
}