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

const int NMAX = 100000;

struct nod
{
    int x;
    nod *next;
};

nod *G[NMAX + 1], *GT[NMAX + 1], *CTC[NMAX + 1];

int N, M, nrc,
    nr, post[NMAX + 1];

bool viz[NMAX + 1];

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

void add(nod *&cap_lst, int nod_ad)
{
    nod *p;
    p = new nod;
    p->x = nod_ad;
    p->next = cap_lst;
    cap_lst = p;
}

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

void DFS(int vf)
{
    viz[vf] = 1;
    for(nod *p = G[vf]; p != NULL; p = p->next)
        if(viz[p->x] == 0)
            DFS(p->x);
    post[++nr] = vf;
}
void DFSt(int vf)
{
    viz[vf] = 0;
    add(CTC[nrc], vf);
    for(nod *p = GT[vf]; p != NULL; p = p->next)
        if(viz[p->x] == 1)
            DFSt(p->x);
}

void componente()
{
    int i;
    for(i = 1; i <= N; i++)
        if(viz[i] == 0)
            DFS(i);
    for(i = N; i >= 1; i--)
        if(viz[post[i]] == 1)
        {
            nrc++;
            DFSt(post[i]);
        }
}
void afis()
{
    g << nrc << '\n';
    for(int i = 1; i <= nrc; i++)
    {
        for(nod *p = CTC[i]; p != NULL; p = p->next)
            g << p->x << ' ';
        g << '\n';
    }
}
int main()
{
    citireGraf();
    componente();
    afis();
    return 0;
}