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

using namespace std;

const int MAX_NODURI = 100005;

vector<int> graf[MAX_NODURI];
vector<int> graf_transpus[MAX_NODURI];
bool vizitat[MAX_NODURI];

vector<int> stiva_ordine; 
vector<vector<int>> componente; 
vector<int> ctc_curent; 

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

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

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

    int n, m;
    fin >> n >> m;
    
    for (int i = 0; i < m; ++i) {
        int u, v;
        fin >> u >> v;
        graf[u].push_back(v);
        graf_transpus[v].push_back(u);
    }

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

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

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

    fout << componente.size() << "\n";
    for (int i = 0; i < componente.size(); ++i) {
        for (int nod : componente[i]) {
            fout << nod << " ";
        }
        fout << "\n";
    }

    fin.close();
    fout.close();

    return 0;
}