#include <iostream>
#include <fstream>

using namespace std;

const int NMAX = 100001;

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

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

bool viz[NMAX];

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

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

void add(nod *&cap_lst, int nod_ad)
{
    nod *p = new nod;

    p->x = nod_ad;
    p->next = cap_lst;
    cap_lst = p;
}

void citiregraf()
{
    int x, y;

    f >> N >> M;

    while(M--)
    {
        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 componente()
{
    int i;

    for(i = 1; i <= N; i++)
        if(!viz[i])
            DFS(i);

    for(i = N; i >= 1; i--)
        if(viz[post[i]])
        {
            nrc++;
            DFSt(post[i]);
        }
}

void afisare()
{
    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();
    afisare();

    f.close();
    g.close();

    return 0;
}