#include <iostream>
#include <vector>
#include <fstream>
#define VMAX 100000
#define EMAX 200000
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");

vector <int> adj[VMAX];
vector <int> aux[VMAX];
vector <int> toate[EMAX];

int V, E, x, y;
//stack <int> st;
bool vis[VMAX];
int stiva[VMAX], lg_stiva;

void DFS(int u)

{
    vis[u] = 1;

    for (int w = 0; w < adj[u].size(); ++w)

        if (!vis[adj[u][w]]) DFS(adj[u][w]);

    stiva[lg_stiva++] = u;

}


void DFS_2(int u, int contor)

{
    vis[u] = true;

    toate[contor].push_back(u);

    for (int w = 0; w < aux[u].size(); ++w)

        if (vis[aux[u][w]] == 0) DFS_2(aux[u][w], contor);
}


int main()

{
    ios_base::sync_with_stdio(false);

    fin.tie(NULL);

    fout.tie(NULL);

    fin >> V >> E;

    for (int i = 0; i < E; i++)

    {
        fin >> x >> y;
        x--, y--;
        adj[x].push_back(y);
        aux[y].push_back(x);
    }

    for (int i = 0; i < V; i++)
        if (vis[i] == false) DFS(i);

    for (int i = 0; i < V; i++)
        vis[i] = false;

    int nr = 0, contor = 0;

    for (int i = lg_stiva - 1; i >= 0; i--)
    {
        x = stiva[i];
        if (vis[x] == false)
        {
            DFS_2(x, contor);
            contor++;
        }
    }

    /*while (!st.empty())
    {
        x = st.top();
        if (vis[x] == false)
        {
            DFS_2(x, contor);
            contor++;
        }
        st.pop();
    }*/

    fout << contor << endl;

    for (int i = 0; i < contor; ++i)
    {
        for (int j = 0; j < toate[i].size(); ++j)
            fout << toate[i][j] + 1 << " ";
        fout << endl;
    }

    fin.close();

    fout.close();

    return 0;

}