#include <iostream>
#include <fstream>
#include <vector>

void DFS(std::vector<int> graph[], bool viz[], int k, std::vector<int> &postordine) {
    viz[k] = true;
    for (size_t i = 0; i < graph[k].size(); i++) {
        if (!viz[graph[k][i]]) {
            DFS(graph, viz, graph[k][i], postordine);
        }
    }
    postordine.push_back(k);
}

void DFST(std::vector<int> graphT[], bool viz[], int k, std::vector<int> components[], int nr) {
    viz[k] = false;
    components[nr].push_back(k);
    for (size_t i = 0; i < graphT[k].size(); i++) {
        if (viz[graphT[k][i]]) {
            DFST(graphT, viz, graphT[k][i], components, nr);
        }
    }
}

void readGraphs(std::vector<int> graph[], std::vector<int> graphT[], int &n, int &m) {
    std::ifstream fin("ctc.in");
    int x, y;
    fin >> n >> m;
    for (size_t i = 0; i < m; i++) {
        fin >> x >> y;
        graph[x].push_back(y);
        graphT[y].push_back(x);
    }
    fin.close();
}

int main(int argc, char *argv[]) {
    int n, m;
    bool viz[5001] = { false };
    int nrComponenteTareConexe = 0;
    std::vector<int> graph[5001], graphT[5001], postordine;
    std::vector<int> components[5001];
    readGraphs(graph, graphT, n, m);
    for (size_t i = 1; i <= n; i++) {
        if (!viz[i]) {
            DFS(graph, viz, i, postordine);
        }
    }
    for (int i = postordine.size(); i >= 0; i--) {
        if (viz[postordine[i]]) {
            nrComponenteTareConexe++;
            DFST(graphT, viz, postordine[i], components, nrComponenteTareConexe);
        }
    }
    std::ofstream fout("ctc.out");
    fout << nrComponenteTareConexe << "\n";
    for (int i = 1; i <= nrComponenteTareConexe; i++) {
        for (int j = components[i].size() - 1; j >= 0; j--) {
            fout << components[i][j] << " ";
        }
        fout << "\n";
    }
    fout.close();
    return 0;
}