#include <fstream>
#include <iostream>
#include <vector>
using namespace std;

const int kNMax = 200010;
int n, index[kNMax], viz[kNMax], link[kNMax], nr = 1;
int nr_sol;
vector <int> G[kNMax], Stack, sol[kNMax];


void Citire() {
    ifstream in("ctc.in");
    int x, y, m;
    in >> n >> m;
    for (int i = 1; i <= m; ++i) {
        in >> x >> y;
        G[x].push_back(y);
    }
    in.close();
}

void Dfs(int nod) {
    int vecin, i;
    viz[nod] = 1;
    index[nod] = nr;
    link[nod] = nr;
    ++nr;
    Stack.push_back(nod);
    for (int i = 0; i < G[nod].size(); ++i){
        vecin = G[nod][i];
        if (!index[vecin]) {
            Dfs(vecin);
            if (link[nod] > link[vecin])
                link[nod] = link[vecin];
        } else if (viz[vecin])
            if (link[nod] > link[vecin])
                link[nod] = link[vecin];
    }
    if (link[nod] == index[nod]) {
        sol[++nr_sol].push_back(Stack.back());
        viz[Stack.back()] = 0;
        while (Stack.back() != nod) {
            Stack.pop_back();
            sol[nr_sol].push_back(Stack.back());
            viz[Stack.back()] = 0;
        }
        Stack.pop_back();
    }
}

void Solve() {
    for (int i = 1; i <= n; ++i)
        if(!index[i])
            Dfs(i);
}

void Afisare() {
    ofstream out("ctc.out");
    out << nr_sol << '\n';
    for (int i = nr_sol; i >= 1; --i) {
        for (int j = sol[i].size() - 1; j >= 0; --j)
            out << sol[i][j] << ' ';
        out << '\n';
    }
    out.close();
}

int main() {
    Citire();
    Solve();
    Afisare();
    return 0;
}