#include <bits/stdc++.h>

#define NMAX 100010
using namespace std;

class Task {
public:
  void solve() {
    read_input();
    // get_result();
    print_output(get_result());
  }

private:
  // n = numar de noduri, m = numar de muchii
  int n, m;

  // adj[node] lista de adiacenta a nodului node
  vector<int> adj[NMAX];
  vector<int> adjt[NMAX];

  void read_input() {
      ifstream in("ctc.in");
      in >> n >> m;

      for (int i = 1; i <= m; ++i) {
          int x, y;
          in >> x >> y;
          adj[x].push_back(y);
          adjt[y].push_back(x);
      }

      in.close();
  }

  void dfs(int node, vector<int> &sort, vector<int> &visited){
      visited[node] = 1;
      for (auto &neighbor : adj[node])
          if (!visited[neighbor]) 
            dfs(neighbor,sort,visited);

      sort.push_back(node);
	}


	void dfs_transpus(int node, vector<int> &current, vector<int> &visited){
      visited[node] = 0;
	  current.push_back(node);

	  for (auto &neighbor : adjt[node])
		  if (visited[neighbor])
			dfs_transpus(neighbor,current,visited);
	}

  vector<vector<int>> get_result() {
      vector<vector<int>> solutie;
      vector<int> visited(n + 1);
      vector<int> sort;
      sort.push_back(-1);

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

      for (int i = n; i >= 1; --i)
			if (visited[sort[i]]) {
				vector<int> current;
				dfs_transpus(sort[i], current, visited);
				solutie.push_back(current);
			}
		
	  return solutie;
  }

  void print_output(vector<vector<int>> result) {
      ofstream out("ctc.out");
	  out << result.size() << '\n';
	  for (const auto& ctc : result) {
		  for (int nod : ctc) {
			out << nod << ' ';
          }
		  out << '\n';
      }

	  out.close();
  }
};

int main() {
  // din cauza ca fac redirectari, salvez starea lui cin si cout
  // auto cin_buff = cin.rdbuf();
  // auto cout_buff = cout.rdbuf();

  // las liniile urmatoare daca citesc din fisier
  // ifstream fin("in");
  // cin.rdbuf(fin.rdbuf()); // save and redirect

  // las liniile urmatoare daca afisez in fisier
  // ofstream fout("out");
  // cout.rdbuf(fout.rdbuf()); //save and redirect

  // aici este rezolvarea propriu-zisa
  Task *task = new Task();
  task->solve();
  delete task;

  // restore pentru cin si cout
  // cin.rdbuf(cin_buff);
  // cout.rdbuf(cout_buff);

  // obs. nu e nevoie sa inchid fisierele
  // cand se apeleaza destructorii pentru fin si fout se vor inchide

  return 0;
}