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

std::vector<int> v[100001], vt[100001], sol[100001];
int n, nrSol;
std::vector<int> postordine;
bool viz[100001] = {false};

void DFS(int k) {
    viz[k] = true;
    for (int i = 0; i < v[k].size(); i++) {
        if (!viz[v[k][i]]) {
            DFS(v[k][i]);
        }
    }
    postordine.push_back(k);
}

void DFST(int k) {
    viz[k] = false;
    sol[nrSol].push_back(k);
    for (int i = 0; i < vt[k].size(); i++) {
        if (viz[vt[k][i]]) {
            DFST(vt[k][i]);
        }
    }
}

void citire() {
    std::ifstream fin("ctc.in");
    int m, x, y;
    fin >> n >> m;
    for (int i = 0; i < m; i++) {
        fin >> x >> y;
        v[x].push_back(y);
        vt[y].push_back(x);
    }
    fin.close();
}

int main(int argc, char *argv[]) {
    citire();

    for (int i = 1; i <= n; i++) {
        if (!viz[i]) {
            DFS(i);
        }
    }
    
    for (int i = postordine.size() - 1; i >= 0; i--) {
        if (viz[postordine[i]]) {
            nrSol++;
            DFST(postordine[i]);
        }
    }
    
    std::ofstream fout("ctc.out");
    fout << nrSol << "\n";
    for (int i = nrSol; i >= 0; i--) {
        for (int j = 0; j < sol[i].size(); j++) {
            fout << sol[i][j] << " ";
        }
        fout << "\n";
    }
    fout.close();
    return 0;
}