#include <fstream>
#include <vector>
#include <queue>

const int NMAX = 100005;

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

int N,M,componenta[NMAX],numar_elemente,stiva[NMAX],elemente_stiva,nr;
vector <int> v[NMAX],vt[NMAX],componente[NMAX];
bool removed[NMAX],used[NMAX],used_aux[NMAX];

void DFS(int nod)
{
    used[nod] = true;
    elemente_stiva++;
    stiva[elemente_stiva] = nod;
    for (int i = 0; i < v[nod].size(); ++i)
    {
        int vecin = v[nod][i];
        if (!used[vecin])
            DFS(vecin);
    }
}

void DFST(int nod)
{
    used_aux[nod] = true;
    elemente_stiva++;
    stiva[elemente_stiva]++;
    if (used[nod])
    {
        componente[nr].push_back(nod);
    }
    for (int i = 0; i < vt[nod].size(); ++i)
    {
        int vecin = vt[nod][i];
        if (!used_aux[vecin])
            DFST(vecin);
    }
}

void search(int nod)
{
    nr++;
    for (int i = 1; i <= elemente_stiva; ++i)
        used[stiva[i]] = false;
    elemente_stiva = 0;
    DFS(nod);
    DFST(nod);

    numar_elemente = componente[nr].size();
    for (int i = 0; i < numar_elemente; ++i)
    {
        removed[componente[nr][i]] = true;
    }
}

void afisare()
{
    g << nr << '\n';
    for (int i = 1; i <= nr; ++i)
    {
        for (int j = 0; j < componente[i].size(); ++j)
            g << componente[i][j] << " ";
        g << '\n';
    }
}

int main()
{
    f >> N >> M;
    for (int i = 1; i <= M; ++i)
    {
        int x, y;
        f >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }

    for (int i = 1; i <= N; ++i)
    {
        if(!removed[i])
        {
            search(i);
        }
    }

    afisare();

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