#include <iostream>
#include <fstream>
#include <vector>
#include <bitset>
#include <algorithm>

using namespace std;

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

struct muchie{
  int a, b;
};

const int N = 1e5;
vector <int> adj[N + 1], adj2[N + 1], componente[N + 1];
vector <int> topo;
bitset <N + 1> viz;

int ind = 1;

muchie muchii[2 * N + 1];

void topo_sort(int nod){
  viz[nod] = 1;
  for(auto vec : adj[nod])
    if(!viz[vec])
      topo_sort(vec);
  topo.push_back(nod);
}

void dfs(int nod){
  componente[ind].push_back(nod);
  viz[nod] = 1;
  for(auto vec : adj[nod])
    if(!viz[vec])
      dfs(vec);
}

int main(){
    int n, m;
    fin >> n >> m;
    for(int i = 1; i <= m; i++){
      int a, b;
      fin >> a >> b;
      adj[a].push_back(b);
      adj2[b].push_back(a);
    }
    for(int i = 1; i <= n; i++)
        if(!viz[i])
          topo_sort(i);
    viz.reset();

    for(int i = n; i >= 1; i--)
      if(!viz[i])
        dfs(i), ind++;
    fout << ind - 1 << '\n';
    for(int i = 1; i <= ind; i++) sort(componente[i].begin(), componente[i].end());
    for(int i = 1; i <= ind; i++, fout << '\n')
      for(auto vec : componente[i])
        fout << vec << ' ';

    return 0;
}