#include <fstream>
#include<vector>
#define NMAX 100002
using namespace std;

ifstream fin("ctc.in");
ofstream fout("ctc.out");

int n, nr, nrc, m;
vector <int> G[NMAX];
vector <int> GT[NMAX];
vector <int> CTC[NMAX];

int postordine[NMAX];
bool uz[NMAX];
int ctc[NMAX];
///ctc[i] = componenta tare conexa din care face parte i;

void citire();
void DFS(int x);
void DFST(int x);
void afisare();

int main()
{
    int i;
    citire();
    for (i = 1; i <= n; i++)
        if (!uz[i]) DFS(i);
    ///etapa II
    for (i = n; i > 0; i--)
        if (!ctc[postordine[i]])
        {
            nrc++;
            DFST(postordine[i]);
        }
    afisare();
    return 0;
}
void citire()
{
    int x, y, i;
    fin >> n >> m;
    for (i = 0; i < m; i++)
    {
        ///arc
        fin >> x >> y;
        G[x].push_back(y);
        ///in graful transpus pun arcul (y, x)
        GT[y].push_back(x);
    }
}
void DFS(int x)
{
    int i;
    uz[x] = 1;
    for (i = 0; i < G[x].size(); i++)
    {
        if (uz[G[x][i]] == 0)
            DFS(G[x][i]);
    }
    nr++;
    postordine[nr] = x;
}
void DFST(int x)
{
    int i;
    ctc[x] = nrc;
    CTC[nrc].push_back(x);
    for (i = 0; i < GT[x].size(); i++)
    {
        if (ctc[GT[x][i]] == 0)
            DFST(GT[x][i]);
    }
}
void afisare()
{
    int i, j;
    fout << nrc << '\n';
    for (i = 1; i <= nrc; i++)
        {
            for (j = 0; j < CTC[i].size(); j++)
                fout << CTC[i][j] << ' ';
        fout << '\n';
        }
}