#include <fstream>
#include <vector>

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

vector<bool> viz;

void dfs(int node, vector<vector<int>>& edges, vector<int>& add_to) {
    viz[node] = true;
    for (auto new_node : edges[node]) {
        if( !viz[new_node] )
            dfs(new_node, edges, add_to);
    }
    add_to.push_back(node);
}

void Solve() {
    int n, m; cin >> n >> m;
    vector<vector<int>> edges(n);
    vector<vector<int>> rev_edges(n);
    for (int i = 0; i < m; i++) {
        int a, b; cin >> a >> b; a--; b--;
        edges[a].push_back(b);
        rev_edges[b].push_back(a);
    }

    viz.resize(n);
    vector<int> st;
    for (int node = 0; node < n; node++) {
        if( !viz[node] ) {
            dfs(node, edges, st);
        }
    }

    viz.clear();
    viz.resize(n);
    vector<vector<int>> ctc;
    for (int i = st.size() - 1; i >= 0; i--) {
        if (viz[st[i]] == 0) {
            ctc.push_back(vector<int>());
            dfs(st[i], rev_edges, ctc.back());
        }
    }

    cout << ctc.size() << "\n";
    for (auto comp : ctc) {
        for (auto node : comp) {
            cout << node + 1 << " ";
        }
        cout << "\n";
    }
}

int main() {
    Solve();
    return 0;
}