#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
typedef vector<vector<int> > GRAPH;
#define DMAX 100005

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

void Read();
void DFS(int node);
void DFS2(int node);

int n, m, ct;
GRAPH G, GT;
vector<bool> viz;
vector<int> ord;
vector<vector<int> > Sol;

int main()
{
    Read();

    for (int i = 1; i <= n; ++i)
        if ( !viz[i] ) DFS(i);

    viz.assign(viz.size()+1, 0);

    for (int i = n; i > 0; --i)
        if ( !viz[ord[i]] )
        {
            ct++;
            DFS2(ord[i]);
        }

    fout << ct << '\n';
    for (int i = 1; i <= ct; ++i)
    {
        for (unsigned int it = 0; it < Sol[i].size(); ++it)
            fout << Sol[i][it] << ' ';
        fout << '\n';
    }

    fin.close();
    fout.close();
    return 0;
}

void DFS(int node)
{
    viz[node] = true;

    vector<int>::iterator it;
    for (it = G[node].begin(); it != G[node].end(); ++it)
        if ( !viz[*it] ) DFS(*it);
    ord.push_back(node);
}

void DFS2(int node)
{
    viz[node] = true;

    Sol[ct].push_back(node);
    vector<int>::iterator it;
    for (it = GT[node].begin(); it != GT[node].end(); ++it)
        if ( !viz[*it] ) DFS2(*it);
}

void Read()
{
    fin >> n >> m;
    G.resize(n+1), GT.resize(n+1), viz.resize(n+1);
    Sol.resize(n+1);
    ord.push_back(0);

    int x, y;
    for (int i = 0; i < m; ++i)
    {
        fin >> x >> y;
        G[x].push_back(y);
        GT[y].push_back(x);
    }

}