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

ifstream f("ctc.in");
ofstream g("ctc.out");
int N, M, post[100001],nr,nrc;
bool viz[100001];
struct nod
{
    int x;
    nod *next;
};
nod *v1[100001],*v2[100001],*cc[100001];

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()
{
    f >> N >> M;
    while(M--)
    {
        int x, y;
        f >> x >> y;
        add(v1[x], y);
        add(v2[y], x);
    }
}

void DFS(int vf)
{
    nod *p;
    viz[vf] = 1;
    for(p = v1[vf]; p != NULL; p = p -> next)
        if(!viz[p -> x])
            DFS(p -> x);
    post[++nr]=vf;
}

void DFSt(int vf)
{
    nod *p;
    viz[vf] = 0;
    add(cc[nrc],vf);
    for(p = v2[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>0;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 = cc[i]; p != NULL; p = p->next)
            g << p->x << ' ';
        g << '\n';
    }
}
int main()
{
    citiregraf();
    componente();
    afis();
    return 0;
}