#include <iostream>
#include <list>
#include <stack>
#include <fstream>
#include <vector>
#define NIL -1

using namespace std;

class Graph {
    int V;
    list<int> *adj;

    void SCCUtil(int u, int disc[], int low[], stack<int> *st, bool stackMember[]);
public:
    Graph(int V);
    void addEdge(int v, int w);
    void SCC();
};

Graph::Graph(int V) {
    this->V = V;
    adj = new list<int>[V];
}

void Graph::addEdge(int v, int w) {
    adj[v].push_back(w);
}

vector< vector<int>* > output;

void Graph::SCCUtil(int u, int disc[], int low[], stack<int> *st, bool stackMember[]) {
    static int time = 0;

    disc[u] = low[u] = ++time;
    st->push(u);
    stackMember[u] = true;

    list<int>::iterator i;
    for (i = adj[u].begin(); i != adj[u].end(); ++i) {
        int v = *i;

        if (disc[v] == -1) {
            SCCUtil(v, disc, low, st, stackMember);

            low[u]  = min(low[u], low[v]);
        } else if (stackMember[v] == true)
            low[u]  = min(low[u], disc[v]);
    }

    int w = 0;
    if (low[u] == disc[u]) {
        vector<int>* out = new vector<int>();

        while (st->top() != u) {
            w = (int) st->top();
            out->push_back(w);
            stackMember[w] = false;
            st->pop();
        }
        w = (int) st->top();
        out->push_back(w);
        stackMember[w] = false;
        st->pop();

        output.push_back(out);
    }
}

void Graph::SCC() {
    int *disc = new int[V];
    int *low = new int[V];
    bool *stackMember = new bool[V];
    stack<int> *st = new stack<int>();

    for (int i = 0; i < V; i++) {
        disc[i] = NIL;
        low[i] = NIL;
        stackMember[i] = false;
    }

    for (int i = 0; i < V; i++)
        if (disc[i] == NIL)
            SCCUtil(i, disc, low, st, stackMember);
}

ifstream fin("ctc.in");
ofstream fout("ctc.out");
#define cin fin
#define cout fout

int main() {
    int n, m;

    cin >> n >> m;
    Graph g(n);
    for (int i = 0; i < m; i++) {
        int x, y;
        cin >> x >> y;
        g.addEdge(x - 1, y - 1);
    }
    g.SCC();

    cout << output.size() << "\n";
    for (int i = 0; i < output.size(); i++) {
        for (int j = 0; j < output[i]->size(); j++) {
            cout << (*output[i])[j] << " ";
        }
        cout << "\n";
    }

    return 0;
}