#include <fstream>
#include <vector>
#include <stack>

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

const int NMAX = 100000;

int N, M, nrc;

vector < int > G[NMAX + 1], CTC[NMAX + 1];
int D[NMAX + 1], Dmin[NMAX + 1], Timp = 0;

stack < int > S;
bool inSt[NMAX + 1];

void citire() {
    int x, y;
    in >> N >> M;
    for (int i = 1; i <= M; i++) {
        in >> x >> y;
        G[x].push_back(y);
    }
}

void DFS(int x) {
    D[x] = ++Timp;
    Dmin[x] = D[x];
    S.push(x);
    inSt[x] = 1;
    for (auto& y : G[x]) {
        if (D[y] == 0) {
            DFS(y);
            Dmin[x] = min(Dmin[x], Dmin[y]);
        }
        else {
            if (inSt[y] == 1)
                Dmin[x] = min(Dmin[x], D[y]);
        }
    }

    if (Dmin[x] == D[x]) {
        int u;
        nrc++;
        do {
            u = S.top();
            CTC[nrc].push_back(u);
            S.pop();
            inSt[u] = 0;
        } while (x != u);
    }
}

void afisare() {
    out << nrc << '\n';
    for (int i = 1; i <= nrc; i++) {
        for (auto& x : CTC[i])
            out << x << ' ';
        out << '\n';
    }
}

int main(){
 
    citire();
    for (int i = 1; i <= N; i++)
        if (D[i] == 0)
            DFS(i);

    afisare();
    in.close();
    out.close();

    return 0;
}