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

using namespace std;

const int MAXN = 100005;

vector<int> adj[MAXN];
vector<int> adj_rev[MAXN];
bool visited[MAXN];
vector<int> order;

vector<vector<int>> ctc;
vector<int> current_comp;

void dfs1(int u) {
    visited[u] = true;
    for (int v : adj[u]) {
        if (!visited[v]) {
            dfs1(v);
        }
    }
    order.push_back(u);
}

void dfs2(int u) {
    visited[u] = true;
    current_comp.push_back(u);
    for (int v : adj_rev[u]) {
        if (!visited[v]) {
            dfs2(v);
        }
    }
}

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

    int n, m;
    cin >> n >> m;

    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj_rev[v].push_back(u);
    }

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

    // Resetăm vectorul de vizitat
    for (int i = 1; i <= n; ++i) {
        visited[i] = false;
    }

    while (!order.empty()) {
        int u = order.back();
        order.pop_back();

        if (!visited[u]) {
            current_comp.clear();
            dfs2(u);
            ctc.push_back(current_comp);
        }
    }

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

    return 0;
}