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

using namespace std;

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

vector<vector<int>> grInit;
vector<vector<int>> grTranspus;
vector<int> viz;
stack<int> st;
vector<vector<int>> compConexe;
int idx = 0;

void dfsInitial(int x) {
    viz[x] = 1;
    for (int& y : grInit[x]) {
        if (viz[y] == 0) {
            dfsInitial(y);
        }
    }
    st.push(x);
}

void dfsTranspus(int x) {
    viz[x] = 1;
    compConexe[idx].push_back(x);
    for (int& y : grTranspus[x]) {
        if (viz[y] == 0) {
            dfsTranspus(y);
        }
    }
}


int main() {

    int N, M;
    fin >> N >> M;
    grInit.resize(N + 1);
    grTranspus.resize(N + 1);

    for (int i = 0; i < M; i++) {
        int x, y;
        fin >> x >> y;
        grInit[x].push_back(y);
        grTranspus[y].push_back(x);
    }

    viz.assign(N + 1, 0);
    for (int i = 1; i <= N; i++) {
        if (viz[i] == 0) {
            dfsInitial(i);
        }
    }

    viz.assign(N + 1, 0);
    compConexe.resize(N + 1);
    while (!st.empty()) {
        int crt = st.top();
        st.pop();
        if (viz[crt] == 0) {
            dfsTranspus(crt);
            idx++;
        }
    }

    fout << idx << endl;
    for (int i = 0; i < idx; i++) {
        for (auto& c : compConexe[i]) {
            fout << c << ' ';
        }
        fout << endl;
    }
    
    return 0;
}