#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

const int Nmax = 100000;
vector <int> adj[Nmax + 1];
vector <int> adj_rev[Nmax + 1];
vector <int> order;
vector <int> comp;
bool viz[Nmax + 1];

void dfs1(int node)
{
    viz[node] = true;
    for (auto u : adj[node])
    {
        if (!viz[u])
        {
            dfs1(u);
        }
    }
    order.push_back(node);
}

void dfs2(int node)
{
    viz[node] = true;
    comp.push_back(node);
    for (auto u : adj_rev[node])
    {
        if (!viz[u])
        {
            dfs2(u);
        }
    }
}

int main()
{
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    int n, m;
    fin >> n >> m;
    for (int i = 1; i <= m; i++)
    {
        int u, v;
        fin >> u >> v;
        adj[u].push_back(v);
        adj_rev[v].push_back(u);
    }
    for (int i = 1; i <= n; i++)
    {
        if (!viz[i])
        {
            dfs1(i);
        }
    }
    reverse(order.begin(), order.end());
    for (int i = 1; i <= n; i++)
    {
        viz[i] = false;
    }
    int cnt = 0;
    for (auto u : order)
    {
        if (!viz[u])
        {
            dfs2(u);
            cnt++;
            comp.clear();
        }
    }
    fout << cnt << "\n";
    for (int i = 1; i <= n; i++)
    {
        viz[i] = false;
    }
    for (auto u : order)
    {
        if (!viz[u])
        {
            dfs2(u);
            for (auto u : comp)
            {
                fout << u << " ";
            }
            fout << "\n";
            comp.clear();
        }
    }
    return 0;
}