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

char uz[NMAX];
char v1[NMAX], v2[NMAX];
int nr[NMAX];
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 DFS(int, char[], 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()
{
    //DFS pentru graful initial
    //DFS pentru graful transpus
    int i, j;
    Lista q;
    for (i=1; i<=n; ++i)
        if (!uz[i])
        {
            ++nr_ctc;
            DFS (i, v1, 0);
            DFS (i, v2, 1);
            for (j=1; j<=nr[0]; ++j)
            {
                if (v1[nr[j]] && v2[nr[j]] && !uz[nr[j]])
                {
                    inserare(CTC[nr_ctc], NULL, nr[j]);
                    uz[nr[j]]=nr_ctc;//se afla intr-o componenta conexa
                }
                v1[nr[j]]=v2[nr[j]]=0;
            }
            nr[0]=0;
        }
    //afisez componentele tare 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 DFS (int vf, char v[], int care)
{
    Lista q;
    if (!care) nr[++nr[0]]=vf;
    v[vf]=1;//acest varf este accesibil
    if (!care) q=A[vf];
        else q=AT[vf];

    for ( ; q; q=q->urm)
        if (!v[q->inf])
            DFS (q->inf, v, care);
    return;
}

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;
}