#include <fstream>
#include <vector>

#define MAX 100005

using namespace std;

int N, M, k, viz[MAX], ctc[MAX];
vector<int> Gi[MAX], Go[MAX], discovered, V[MAX];

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

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

void DFS(int nod, int ind) {
    ctc[nod] = ind;
    for(size_t i =0 ; i < Gi[nod].size(); i++) {
        int dest = Gi[nod][i];
        if(!ctc[dest]) DFS(dest, ind);
    }
}

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]) DFS(nod, ++k);
    }
    for(int i = 1; i <= N; i++)
        V[ctc[i]].push_back(i);
}

void afisare() {
    ofstream out("ctc.out");
    out<<k<<"\n";
    for(int i = 1; i <= k; i++) {
        for(size_t j = 0; j < V[i].size(); j++) out<<V[i][j]<<" ";
        out<<"\n";
    } out.close();
}

int main() {
    citire();
    solve();
    afisare();
    return 0;
}