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

void dfs(int node, vector<int> vis, vector<vector<int>> la, vector<int> s) 
{
    vis[node] = 1;
    for (auto i : la[node])
        if (!vis[i]) dfs(i, vis, la, s);
    s.push_back(node);
}

void revDfs(int node, vector<int> vis, vector<vector<int>> scc, vector<vector<int>> transp, int nr_comp) 
{
    vis[node] = 0;
    scc[nr_comp].push_back(node);
    for (auto i : transp[node])
        if (vis[i])
            revDfs(i, vis, scc, transp, nr_comp);
}

int main() 
{
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");
    vector<int> vis, s, v;
    int n, m, nr_comp = 0;

    fin >> n >> m;
    vector<vector<int>> la(n), transp(n), scc;
    for (int i = 0; i < m; i++) 
    {
        int x, y;
        fin >> x >> y;
        la[x].push_back(y);
        transp[y].push_back(x);
    }

    fin.close();

    for (int i = 0; i < n; i++)
        if (!vis[i]) 
            dfs(i, vis, la, s);

    while (!s.empty()) 
    {
        int node = s.back();
        s.pop_back();
        if (vis[node]) 
        {
            scc.push_back(v);
            revDfs(node, vis, scc, transp, nr_comp);
            nr_comp++;
        }
    }

    fout << nr_comp<< endl;

    for (auto i : scc) 
    {
        for (auto j : i) 
            fout << j << " ";
        fout << endl;
    }
    fout.close();
}