#include <fstream>
#include <vector>

using namespace std;

const int MAX = 101101;

int N, M;

bool Viz[MAX], ctc[MAX];

vector<int> discovered, V;
vector<int> GIn[MAX], GOut[MAX];
vector< vector<int> > CTC;

void citire() {
    ifstream in("ctc.in");
    in >> N >> M;
    for(int i = 1, A, B; i <= M; i++) {
        in >> A >> B;
        GIn[B].push_back(A);
        GOut[A].push_back(B);
    } in.close();
}

void DFF(int nod) {
    Viz[nod] = true;
    for(size_t i = 0; i < GOut[nod].size(); i++) {
        int dest = GOut[nod][i];
        if(!Viz[dest])
            DFF(dest);
    } discovered.push_back(nod);
}

void DFB(int nod) {
    ctc[nod] = true;
    V.push_back(nod);
    for(size_t i = 0; i < GIn[nod].size(); i++) {
        int dest = GIn[nod][i];
        if(!ctc[dest])
            DFB(dest);
    }
}

void solve() {
    for(int i = 1; i <= N; i++) {
        if(!Viz[i]) {
            DFF(i);
        }
    }
    for(; discovered.size(); discovered.pop_back()) {
        int nod = discovered.back();
        if(!ctc[nod]) {
            V.clear();
            DFB(nod);
            CTC.push_back(V);
        }
    }
}

void afisare() {
    ofstream out("ctc.out");
    out << CTC.size() << "\n";
    for(size_t i = 0; i < CTC.size(); i++) {
        for(size_t j = 0; j < CTC[i].size(); j++) {
            out << CTC[i][j] << " ";
        } out << "\n";
    } out.close();
}


int main() {
    citire();
    solve();
    afisare();
}