#include <fstream>
#include <vector>
#define NMAX 100001
using namespace std;

ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

int n, poz;
///graful G reprezentat prin liste de adiacenta
vector <int> G[NMAX];

///graful transpus GT reprezentat prin liste de adiacenta
vector <int> GT[NMAX];

bool viz[NMAX];
int nr; ///nr de componente tare-conexe
vector <int> ctc[NMAX];

int postordine[NMAX];

void citire();
void DFS(int x);
void DFST(int x);
void afis();

int main()
{
    int i;
    citire();
///parcurg dfs graful G, retinand varfurile in postordine
    for (i=1; i<=n; i++)
        if (viz[i]==0)
            DFS(i);

///parcurg vectorul postordine de la dr la st si fac DFST in GT
    for (i=n; i>0; i--)
        if (viz[postordine[i]]==1) ///acest varf este nevizitat in GT
        {
            nr++;
            DFST(postordine[i]);
        }
    afis();
    return 0;
}


void citire()
{
    int i, x, y, m;

    fin>>n>>m;
    for (i=0; i<m; i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }
}

void DFS(int x)
{
    int i;

    viz[x]=1;
    ///parcurg lista de adiacenta a lui x
    for (i=0; i<G[x].size(); i++)
        if (viz[G[x][i]]==0)
            DFS(G[x][i]);
    postordine[++poz]=x;
}

void DFST(int x)
{
    int i, poz;

    viz[x]=0; ///retin acest varf in componenta conexa curenta
    ctc[nr].push_back(x);
    ///parcurg lista de adiacenta a lui x
    for (i=0; i<GT[x].size(); i++)
        if (viz[GT[x][i]]==1)
            DFST(GT[x][i]);
}

void afis()
{
    int i, j ;
    fout<<nr<<'\n';
    for (i=1; i<=nr; i++)
    {
        for (j=0; j<ctc[i].size(); j++)
            fout<<ctc[i][j]<<' ';
        fout<<'\n';
    }
}