#include<bits/stdc++.h>
using namespace std;

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


int main() {
    int nodes, edges;
    fin >> nodes >> edges;
    vector<int> adj[nodes + 1], tadj[nodes + 1];
    vector<int> order;
    for (int i = 1; i <= edges; ++i) {
        int u, v;
        fin >> u >> v;
        //cout << u << " " << v << endl;
        adj[u].push_back(v);
        tadj[v].push_back(u);
    }
    vector<bool> visited(nodes + 1, false);
    function<void(int)> dfs = [&](int u) {
        visited[u] = true;
        for (int v : adj[u]) {
            if (!visited[v]) {
                dfs(v);
            }
        }
        order.push_back(u);
    };
    for (int i = nodes; i > 0; --i) {
        if (!visited[i]) {
            dfs(i);
        }
    }
    reverse(order.begin(), order.end());
    vector<vector<int>> compenets;
    for (int i = nodes ; i > 0; --i) {
        visited[i] = false;
    }
    function<void(int)> dfs2 = [&](int u) {
        visited[u] = true;
        compenets.back().push_back(u);
        for (int v : tadj[u]) {
            if (!visited[v]) {
                dfs2(v);
            }
        }
    };
    for (int i = 0; i < nodes; ++i) {
        if (!visited[order[i]]) {
            compenets.push_back(vector<int>());
            dfs2(order[i]);
        }
    }
    fout << compenets.size() << endl;
    for (auto &v : compenets) {
        for (int u : v) {
            fout << u << " ";
        }
        fout << endl;
    }
}