#include <bits/stdc++.h>
using namespace std;
#define NMAX 100001

	

class Task {
 public:
    void solve() {
        read_input();
        print_output(get_result());
    }

 private:
    int n, m;
    vector<int> lista_vecini[NMAX];
    vector<int> lista_vecini_graf_transpus[NMAX];

    void read_input() {
        ifstream in("ctc.in");
        in >> n >> m;

        for (int i = 1; i <= m; i++) {
            int x, y;
            in >> x >> y;
            lista_vecini[x].push_back(y);
            lista_vecini_graf_transpus[y].push_back(x);
        }

        in.close();
    }

    void dfs(int source, vector<bool> &visited, vector<int> &finish_sort) {
        visited[source] = 1;
        for (auto &vecin : lista_vecini[source]) {
            if (!visited[vecin]) {
                dfs(vecin, visited, finish_sort);
            }
        }

        finish_sort.push_back(source);
    }

 

    void dfs_transpus(int source, vector<bool> &visited, vector<int> &componenta_noua) {
        componenta_noua.push_back(source);
        visited[source] = 0;

        for (auto &vecin: lista_vecini_graf_transpus[source]) {
            if (visited[vecin]) {
                dfs_transpus(vecin, visited, componenta_noua);
            }
        }
    }

    vector<vector<int>> get_result() {
        vector<vector<int>> componente_biconexe;
        std::vector<int> finish_sort;
        vector<bool> visited(n + 1, 0);
        
        finish_sort.push_back(-1);

        for (int i = 1; i <= n; ++i) {
            if (!visited[i]) {
                dfs(i, visited, finish_sort);
            }
        }

        for (int i = n; i > 0; --i) {
            if (!visited[finish_sort[i]]) {
                vector<int> componenta_noua;
                dfs_transpus(finish_sort[i], visited, componenta_noua);
                componente_biconexe.push_back(componenta_noua);
            }
        }

        return componente_biconexe;
    }

    void print_output(vector<vector<int>> componente_biconexe) {
        ofstream out("ctc.out");   
        out << componente_biconexe.size() << "\n";

        for (const auto &ctc : componente_biconexe) {
            for (auto &elem : ctc) {
                out << elem << " ";
            }
            out << "\n";
        }

        out.close();
    }
};
	

int main() {
    Task* task = new Task();
    task->solve();
    delete(task);
    return 0;
}