#include <fstream>

using namespace std;

ifstream f ("ctc.in");
ofstream g ("ctc.out");

const int nedefinit = 0;

struct nod
{
    int info;
    nod *adr;
} *v[100005];

void adauga (int node, int info)
{
    nod *c;
    c = new nod;
    c -> info = info;
    c -> adr = v[node];
    v[node] = c;
}

struct nod_stiva
{
    int info;
    nod_stiva *adr;
} *s;

void adauga_stiva (int info)
{
    nod_stiva *c;
    c = new nod_stiva;
    c -> info = info;
    c -> adr = s;
    s = c;
}

void elimina ()
{
    nod_stiva *d;
    d = s;
    s = s -> adr;
    delete d;
}

int n, m, indecs = 0, nrc = 0;
int index[100005], lowlink[100005], componente[200005];
bool folosit[100005];

void citire ()
{
    f >> n >> m;

    int x, y;

    for (int i = 1; i <= m; i ++)
    {
        f >> x >> y;
        adauga (x, y);
    }

}

int minim (int a, int b)
{
    if (a < b)
        return a;
    return b;
}

void conecteaza (int node)
{
    index[node] = ++ indecs;
    lowlink[node] = indecs;
    adauga_stiva (node);

    nod *c;
    c = v[node];

    while (c)
    {
        if (index[c -> info] == nedefinit)
        {
            conecteaza (c -> info);
            lowlink [node] = minim (lowlink[node], lowlink[c -> info]);
        }
        else if(! folosit [c -> info])
            lowlink[node] = minim (lowlink[node], index[c -> info]);

        c = c -> adr;
    }

    if (index[node] == lowlink[node])
    {
        ++ nrc;
        int poz = ++ componente[0];

        while (s -> info != node)
        {
            componente [++componente[0]] = s -> info, ++ componente[poz];
            elimina ();
        }

        componente [++componente[0]] = s -> info, ++ componente[poz];
        elimina ();
    }
}

void tarjan ()
{
    for (int i = 1; i <= n; i ++)
        if (index[i] == nedefinit)
            conecteaza (i);
}

void afisare ()
{
    g << nrc << '\n';

    int poz = 1, start;
    int curent = componente[poz];


    while (poz <= componente[0])
    {
        ++ poz;
        start = poz;

        for (poz = start; poz <= start + curent - 1; poz ++)
            g << componente[poz] << " ";
        g << '\n';

        curent = componente[poz];
    }
}

int main()
{
    citire ();
    tarjan ();
    afisare ();

    f.close ();
    g.close ();
    return 0;
}