#include <fstream>
#include <vector>
#define NMAX 100001
using namespace std;
ifstream fin ("ctc.in");
ofstream fout ("ctc.out");

int n, nr, nrc;
//graful initial reprezentat prin liste de adiacente
vector<int> G[NMAX];
//graful transpus reprezentat prin liste de adiacente
vector<int>GT[NMAX];
int post[NMAX];
bool viz[NMAX];
vector<int>ctc[NMAX];//ctc[i] contine vb fin componenta tare conexa i
void citire();
void DFS (int x);
void DFST (int x);
void afisare();

int main()
{
    int i;
     citire();
     //parcurgem DFS pe G si contruiesc vectorulpost
     for (i=1; i<=n; i++)
        if(!viz[i]) DFS(i);
        //parcurg vect post de la dreapta sa stanga si DFS in GT
        for (i=n; i>0; i--)
            if(viz[post[i]]) //post[i] este nevizitat in GT
            {
                //am identificat o noua comp conexa
                nrc++;
                DFST(post[i]);
            }
    //afisare
    afisare();
    return 0;
}
void citire()
{
    int m, i, x, y;
    fin>>n>>m;
    for (i=0; i<m; i++)
    {
        fin>>x>>y;
        //exista arc de la x la y in G
        G[x].push_back(y);
        //existA ARC DE LA Y LA X IN gt
        GT[y].push_back(x);
    }
}
void DFS (int x)
{
    int i;
    viz[x]=1;
    //parcurg lista de adiacenta a lui x
    for (i=0; i<G[x].size(); i++)
        if (!viz[G[x][i]]) DFS(G[x][i]);
    post[++nr]=x;
}
void DFST (int x)
{
    int i;
    viz[x]=0;
    ctc[nrc].push_back(x);
    for (i=0; i<GT[x].size(); i++)
        if (viz[GT[x][i]]) DFST(GT[x][i]);
}
void afisare()
{
    fout<<nrc<<'\n';
    for (int i=1; i<=nrc; i++)
        //afisez nodurile din componenta tare conexa i
    {
        for (int j=0; j<ctc[i].size(); j++)
            fout<<ctc[i][j]<<' ';
        fout<<'\n';
    }
}