#include <iostream>
#include <fstream>
using namespace std;

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

const int NMAX = 100001,
          MMAX = 200001;

struct nod
{
    int info;
    nod *urm;
};
nod *G[NMAX],
    *GT[NMAX],
    *CTC[NMAX];

bool viz[NMAX];
int N, M, S[NMAX], vf, nrc;

void add(nod *&p, int val)
{
    nod *r = new nod;
    r->info = val;
    r->urm = p;
    p = r;
}

void citire()
{
    f >> N >> M;
    for(int i = 1; i <= M; i++)
    {
        int x, y;
        f >> x >> y;
        add(G[x], y);
        add(GT[y], x);
    }
}

void DFS(int Nod)
{
    viz[Nod] = 1;
    for(nod *p = G[Nod]; p; p = p->urm)
        if(!viz[p->info])
            DFS(p->info);
    S[++vf] = Nod;
}

void DFST(int Nod)
{
    viz[Nod] = 0;
    add(CTC[nrc], Nod);
    for(nod *p = GT[Nod]; p; p = p->urm)
        if(viz[p->info])
            DFST(p->info);
}

void afisare()
{
    g << nrc << '\n';
    for(int i = 1; i <= nrc; i++)
    {
        for(nod*p = CTC[i]; p; p = p->urm)
            g << p->info << ' ';
        g << '\n';
    }
}

int main()
{
    citire();
    for(int i = 1; i <= N; i++)
        if(!viz[i])
            DFS(i);
    while(vf)
    {
        int curent = S[vf--];
        if(viz[curent])
        {
            nrc++;
            DFST(curent);
        }
    }
    afisare();
    return 0;
}