#include <fstream>
#include <vector>
#include <cstring>
#include <stack>
using namespace std;

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

const int NMAX = 100000 + 5;

int n, m, nr_componente;
vector<int> G[NMAX], G_transpus[NMAX], componente[NMAX];
stack<int> noduri_procesate;
bool vizitat[NMAX];

void firstDFS(int nod)
{
    vizitat[nod] = true;
    for (int i = 0; i < G[nod].size(); i++)
    {
        int vecin = G[nod][i];
        if (!vizitat[vecin])
            firstDFS(vecin);
    }
    noduri_procesate.push(nod);
}

void secondDFS(int nod)
{
    vizitat[nod] = true;
    componente[nr_componente].push_back(nod);
    for (int i = 0; i < G_transpus[nod].size(); i++)
    {
        int vecin = G_transpus[nod][i];
        if (!vizitat[vecin])
            secondDFS(vecin);
    }
}

// Algoritmul lui Kosaraju

int main()
{
    fin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        int x, y;
        fin >> x >> y;
        G[x].push_back(y);
        G_transpus[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
        if (!vizitat[i])
            firstDFS(i);
    memset(vizitat, 0, sizeof vizitat);
    while (!noduri_procesate.empty())
    {
        int nod = noduri_procesate.top();
        if (!vizitat[nod])
        {
            nr_componente++;
            secondDFS(nod);
        }
        noduri_procesate.pop();
    }
    fout << nr_componente << "\n";
    for (int i = 1; i <= nr_componente; i++)
    {
        for (int j = 0; j < componente[i].size(); j++)
            fout << componente[i][j] << " ";
        fout << "\n";
    }
    return 0;
}