#include <fstream>
using namespace std;

const int NMAX = 100001;

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

int N, M, post[NMAX], nr, nrc; ///POST -> post ordine
///nrc = numarul c.t.c.
bool viz[NMAX];

nod *G[NMAX], *GT[NMAX], *CTC[NMAX]; ///CTC[i] = lista nodurilor din componenta tare conexa cu numarul i

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] == 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();
    f.close();
    g.close();
    return 0;
}