#include <fstream>
#define NMAX 100001
using namespace std;
ofstream fout ("ctc.out");

char uz[NMAX];
char v1[NMAX], v2[NMAX];
int n, m, nr_ctc;

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

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

void inserare(Lista&, Lista, int);
void citire(); void DFS(int, char[], Lista *); void rez();

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

void citire()
{
    ifstream fin ("ctc.in");
    fin>>n>>m;
    int i, x, y;
    for (i=1; i<=m; ++i)
        {
            fin>>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);
        }
    fin.close();
    return;
}

void rez()
{
    //DFS pentru graful initial
    //DFS pentru graful transpus
    int i, j;
    for (i=1; i<=n; ++i)
        if (!uz[i])
        {
            ++nr_ctc;
            DFS (i, v1, A);
            DFS (i, v2, AT);
            for (j=1; j<=n; ++j)//aici se poate optimiza
            {
                if (v1[j] && v2[j])
                    uz[j]=nr_ctc;//se afla intr-o componenta conexa
                v1[j]=v2[j]=0;
            }
        }
    //afisez componentele tare conexe
    fout<<nr_ctc<<"\n";
    for (i=1; i<=nr_ctc; ++i)
    {
        for (j=1; j<=n; ++j)
            if (uz[j]==i)
                fout<<j<<" ";
        fout<<"\n";
    }
    fout.close();
    return;
}

void DFS (int vf, char v[], Lista *A)
{
    Lista q;
    v[vf]=1;//acest varf este accesibil

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