#include <iostream>
#include <vector>
#include <fstream>
#include <algorithm>
#include <queue>

using namespace std;

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

vector <int> Graf[200001],Graf_tr[200001],listaOrd,c_conex[200001];
int viz[200001],v_conex[200005];
int nr_conex = 0;

void dfs(int node)
{
    if (viz[node] == 1)
        return;
    viz[node] = 1;
    for (auto i : Graf[node])
        dfs(i);
    listaOrd.push_back(node);
}

void dfs1(int node, int index_conex)
{
    if (v_conex[node])
        return ;
    v_conex[node] = index_conex;
    c_conex[index_conex].push_back(node);
    for (auto i : Graf_tr[node])
    {
        dfs1(i, index_conex);
    }

}

int main() {
    int n, m, a, b;
    fin >> n >> m;
    for (int i = 0; i < m; i++)
    {
        fin >> a >> b;
        Graf[a].push_back(b);
        Graf_tr[b].push_back(a);
    }
    for (int i = 1; i <= n; i++)
    {
        if (viz[i] != 1)
        {
            dfs(i);
        }
    }
    for (int i = n - 1; i >= 0; i--)
    {
        if (!v_conex[listaOrd[i]])
        {
            nr_conex++;
            dfs1(listaOrd[i], nr_conex);
         }
    }
    fout << nr_conex << endl;
    for (int i = 1; i <= nr_conex; i++)
    {
        for (auto j : c_conex[i])
        {
            fout << j << " ";
        }
        fout << endl;
    }

    return 0;
}