#include <fstream>
const int NMAX = 100000;
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
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];
void add(nod*& cap_lst, int nod_add) {
    nod* p;
    p = new nod;
    p->x = nod_add;
    p->next = cap_lst;
    cap_lst = p;
}

void citireGraf() {
    f >> N >> M;
    while (M--) {
        int x, y;
        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])
            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])
            DFSt(p->x);
}


void componentectc()
{
    int i;
    for (int 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();
    componentectc();
    afis();
    return 0;
}