#include <bits/stdc++.h>
#define NMAX 1000001

using namespace std;

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

///graful Gliste de adiacenta in stl
int n, m, start, aux, suma=0, poz=1, nr;
vector<int> G[NMAX];
///graful transpus GT reprezentat prin liste de adiacenta
vector<int> GT[NMAX];
bool viz[NMAX];
vector<int> ctc[NMAX];
int postordine[NMAX];


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

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
    for(i=n; i>0; i--)
        if(viz[postordine[i]]==1)
        {
            nr++;
            DFST(postordine[i]);
        }
    afisare();
    return 0;
}

void citire()
{
    int i, x, y;
    fin>>n>>m;
    for(i=1; 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;
    viz[x] = 0; ///ertin acest vf 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 afisare()
{
    fout<<nr<<'\n';
    for(int i=1; i<=nr; i++)
    {
        for(int j=0; j<ctc[i].size(); j++)
            fout<<ctc[i][j]<<' ';
        fout<<'\n';
    }
}