#include <bits/stdc++.h>
using namespace std;
#define directed true
#define undirected false
#define weighted true
#define unweighted false

const int nmax = 105;
/*class Edge{
    int i, j, cost;
    Edge(int _i, int _j, int _cost) : i(_i), j(_j), cost(_cost){}

    friend bool operator<(const Edge& e1, const Edge& e2) {
          return e1.cost < e2.cost;
    }
    // util in ordonarea dupa cost
};
// o structura de tip muchie, utila in problema APM cand, aplicand algoritmul lui Kruskall
// avem nevoie sa sortam muchiile crescator dupa cost
*/

// in principiu util doar pt HavelHakimi
void countSort(vector<int> &input)
{
    map<int, int> freq;
    for (int x: input) {
        freq[x]++;
    }
    int i = 0;
    for (auto p: freq)
    {
        while (p.second--) {
            input[i++] = p.first;
        }
    }
}

bool HavelHakimi(vector<int> d){
        int n = d.size();
        int sum = 0;
        for(auto degree: d) {
            if(degree > n - 1)
                return false;
            sum += degree;
        }

        while(d.size()){
            countSort(d);
            int biggest = d[0];
            d.erase(d.begin());
            for(int i = 0; i < biggest; ++i)
                {
                    --d[i];
                    if(d[i] < 0){
                        return false;
                    }
                }
            }
        return true;
    }

class Graph {
public:
    int V;
    int E;
    bool dir;
    bool wgt;
    Graph(bool, bool);
    // constructorul care contine doar informatii de tipul
    // 'graful este orientat/neorientat si are/n-are costuri pe muchii'
    void build(int, int, vector<vector<pair<int, int>>>);
    vector<vector<pair<int, int>>> adj;
    // lista de adiacenta a nodului 'n' e formata din perechi de tipul
    // {vecin, cost}, unde cost = costul muchiei {n, vecin}.
    // daca graful n-are costuri pe muchii cost = 0;
    void DFSUtil(int, vector<bool>&, vector<int>&);
    vector<int> DFS(int, vector<bool>&);
    int cc(int);
    pair<vector<int>, vector<int>> bfs(int src);
    // returnez ordinea parcurgerii bfs, dar si
    // un vector de distante minime. Amandoua sunt relevante
    // si specifice parcurgerii in latime
    vector<int> topoSort();
    void dfForTopoSort(int, vector<bool>&, stack<int>&);
    void DFtranspose(vector<vector<pair<int, int>>>, vector<vector<int>>&, int, vector<bool>&);
    vector<vector<int>> Kosaraju();
};

Graph::Graph(bool _directed, bool _weighted) : dir(_directed), wgt(_weighted) {
}

void Graph::build(int _V, int _E, vector<vector<pair<int, int>>> _adj) {
    V = _V;
    E = _E;
    adj = _adj;
}

void Graph::DFSUtil(int v, vector<bool>& vis, vector<int>& island){
    for(auto i : adj[v]){
        int ngb = i.first;
        if(!(vis[ngb])) {
            island.push_back(ngb);
            vis[ngb] = true;
            DFSUtil(ngb, vis, island);
        }
    }
}
vector<int> Graph::DFS(int src, vector<bool>& vis) {
    vector<int> island;
    DFSUtil(src, vis, island);
    return island;
}

int Graph::cc(int src) {
    int nrIslands = 0;
    vector<bool> vis;
    vis.resize(V + 1, false);
    for(int i = 1; i <= V; ++i) {
        if(!vis[i]){
            ++nrIslands;
            DFS(i, vis);
        }
    }
    return nrIslands;
}

// returnez un vector al distantelor minime
// dar si un vector ce contine ordinea parcurgerii bfs
pair<vector<int>, vector<int>> Graph::bfs(int src) {
     pair<vector<int>, vector<int>> toReturn;
     queue<int> q;
     q.push(src);
     vector<int> bfsOrder;
     vector<int> dist;
     dist.resize(V + 1, -1);
     q.push(src);
     dist[src] = 0;
     while(!(q.empty())){
         int dad = q.front();
         bfsOrder.push_back(dad);
         q.pop();
         for(auto i : adj[dad]) {
             int ngb = i.first;
             if(dist[ngb] == - 1){
                  dist[ngb] = dist[dad] + 1;
                  q.push(ngb);
            }
        }
    }
    toReturn.first = dist;
    toReturn.second = bfsOrder;
    return toReturn;
}

void Graph::dfForTopoSort(int src, vector<bool>& vis, stack<int>& st) {
    for(auto i: adj[src]) {
        int ngb = i.first;
        if(vis[ngb] == false) {
            vis[ngb] = true;
            dfForTopoSort(ngb, vis, st);
        }
    }
    st.push(src);
}

vector<int> Graph::topoSort(){
    vector<bool> vis;
    stack<int> st;
    vis.resize(V + 1, false);
    for(int i = 1; i <= V; ++i)
         if(!vis[i]) {
            vis[i] = true;
            dfForTopoSort(i, vis, st);
        }
    vector<int> topoSorted;
    while(st.size()) {
        topoSorted.push_back(st.top());
        st.pop();
    }
    return topoSorted;
}


void Graph::DFtranspose(vector<vector<pair<int, int>>> adjT, vector<vector<int>>& sol, int node, vector<bool>& visT){
    //cout << "totomeda\n";
    sol[sol.size() - 1].push_back(node);
    visT[node] = true;
    for(auto i: adjT[node]) {
            int ngb = i.first;
            if(visT[ngb] == false)
            {
                DFtranspose(adjT, sol, ngb, visT);
            }
        }
}

vector<vector<int>> Graph::Kosaraju() {
    vector<vector<pair<int, int>>> adjT;
    adjT.resize(V + 1);
    for(int i = 1; i <= V; ++i)
        for(auto ngb : adj[i])
            adjT[ngb.first].push_back(make_pair(i, 0));

    vector<bool> visT;
    vector<bool> vis;

    visT.resize(V + 1, false);
    vis.resize(V + 1, false);

    stack<int> st;
    vector<vector<int>> stronglyCC;
    for(int i = 1; i <= V; ++i)
        if(!vis[i])
            {
                vis[i] = true;
                dfForTopoSort(i, vis, st);
                // construim stiva specifica sortarii topologice
            }

    stronglyCC.push_back(vector<int>());
     while(st.size())
        {
            int k = 0;
            while(st.size() && visT[st.top()] == true)
                st.pop();
            if(st.size())
                k = 1;
            if(st.size())
            {
                int crt = st.top();
                DFtranspose(adjT, stronglyCC, crt, visT);
            }
            if(k == 1)
                stronglyCC.push_back(vector<int>());
            if(st.size())
                st.pop();
        }
    return stronglyCC;
}

int main()
{
    /*
    // problema dfs pe pe infoarena
    // https://www.infoarena.ro/problema/dfs
    ifstream fin("dfs.in");
    ofstream fout("dfs.out");
    int v, e;
    fin >> v >> e;
    vector<vector<pair<int, int>>> adj;
    adj.resize(v + 1);
    Graph g(undirected, unweighted);
    for(int i = 1; i <= e; ++i) {
        int src, dst;
        fin >> src >> dst;
        adj[src].push_back(make_pair(dst, 0));
        adj[dst].push_back(make_pair(src, 0));
    }
    g.build(v, e, adj);
    fout << g.cc(1);
    */

    // problema bfs de pe infoarena
    // https://www.infoarena.ro/problema/bfs

    /*
    // problema Sortare topologica de pe infoarena
    // https://www.infoarena.ro/problema/sortaret
    ifstream fin("sortaret.in");
    ofstream fout("sortaret.out");

    int v, e, start;
    Graph g(directed, unweighted);
    vector<vector<pair<int, int>>> adj;
    fin >> v >> e;
    adj.resize(v + 1);
    for(int i = 1; i <= e; ++i) {
         int src, dst;
         fin >> src >> dst;
         adj[src].push_back(make_pair(dst, 0));
    }
    g.build(v, e, adj);
    vector<int> topoOrder = g.topoSort();
    for(auto v: topoOrder)
        fout << v << ' ';
    fout << '\n';
    */

    /* pentru HavelHakimi, in vectorul 'forHavelHakimi'
    punem secventa de numere despre care vrem sa vedem
    daca poate reprezenta secventa gradelor unui graf
    vector<int> forHavelHakimi = {1, 2, 1};
    cout << HavelHakimi(forHavelHakimi);
    */


    /*
    */

    Graph g(true, true);
    ifstream fin("ctc.in");
    ofstream fout("ctc.out");

    int v, e;
    vector<vector<pair<int, int>>> adj;
    fin >> v >> e;
    adj.resize(v + 1);

    for(int i = 1; i <= e; ++i) {
        int src, dst;
        fin >> src >> dst;
        adj[src].push_back(make_pair(dst, 0));
    }

    g.build(v, e, adj);
    vector<vector<int>> SOL = g.Kosaraju();
    fout << SOL.size() << '\n';
    for(int i = 0; i < SOL.size(); ++i)
       {
        for(int j = 0; j < SOL[i].size(); ++j)
            fout << SOL[i][j] << ' ';
        fout << '\n';
       }

    return 0;
}