// CTC Kosaraju

#include <fstream>
#include <vector>

using namespace std;

#define NMAX 100010

class Task {

public:
	void solve() {
		read_input();
		get_result();
		print_output();
	}
private:
	vector<int> adj[NMAX];
	vector<int> adj_trans[NMAX];
	vector<vector<int>> ctc;
	vector<int> viz;
	vector<int> topsort;
	int n, m;

	void read_input() {
		ifstream fin("ctc.in");
		fin >> n >> m;
		viz = vector<int> (n + 1, 0);

		int x, y;
		topsort.push_back(-1);
		for (int i = 0; i < m; ++i) {
			fin >> x >> y;
			adj[x].push_back(y);
			adj_trans[y].push_back(x);
		}
		fin.close();
	}

	void get_result() {
		for (int i = 1; i <= n; ++i) {
			if (viz[i] == 0) {
				dfs(i);
			}
		}

		for (int i = n; i >= 1; --i) {
			if (viz[topsort[i]] == 1) {
				vector<int> new_comp;
				dfs_trans(topsort[i], new_comp);
				ctc.push_back(new_comp);
			}
		}
	}

	void dfs(int node) {
		viz[node] = 1;
		for (int neighbour : adj[node]) {
			if (viz[neighbour] == 0) {
				dfs(neighbour);
			}
		}
		topsort.push_back(node);
	}

	void dfs_trans(int node, vector<int>& comp) {
		viz[node] = 0;
		comp.push_back(node);
		for (int neighbour : adj_trans[node]) {
			if (viz[neighbour] == 1) {
				dfs_trans(neighbour, comp);
			}
		}
	}

	void print_output() {
		ofstream fout("ctc.out");
		fout << ctc.size() << "\n";
		for (vector<int> comp : ctc) {
			for (int el : comp) {
				fout << el << " ";
			}
			fout << "\n";
		}
		fout.close();
	}
};

int main() {
	Task* task = new Task();
	task->solve();
	delete task;
	return 0;
}