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

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

const int nmax = 100001;

vector<int> graf[nmax];
vector<int> transpus[nmax];

vector<int> ordine;
vector<int> componenta;

bool vizitat[nmax];

void dfs1(int nod){
    vizitat[nod] = true;
    for (int vecin : graf[nod]){
        if (!vizitat[vecin])
            dfs1(vecin);
    }
    ordine.push_back(nod);
}

void dfs2(int nod){
    vizitat[nod] = true;
    componenta.push_back(nod);
    for (int vecin : transpus[nod]){
        if (!vizitat[vecin])
            dfs2(vecin);
    }
}

int main(){
    int n, m;
    fin >> n >> m;
    for (int i = 0; i < m; i++){
        int x, y;
        fin >> x >> y;
        graf[x].push_back(y);
        transpus[y].push_back(x);
    }

    for (int i = 1; i <= n; i++){
        if (!vizitat[i])
            dfs1(i);
    }

    for (int i = 1; i <= n; i++)
        vizitat[i] = false;

    vector<vector<int>> componente;

    for (int i = (int)ordine.size() - 1; i >= 0; i--){
        int nod = ordine[i];
        if (!vizitat[nod]){
            componenta.clear();
            dfs2(nod);
            componente.push_back(componenta);
        }
    }

    fout << componente.size() << '\n';

    for (auto comp : componente){
        for (int nod : comp)
            fout << nod << " "; 
        fout << '\n';
    }

    return 0;
}