#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

const int N = 1e5 + 5;

vector<int> nxt[N], prv[N], con[N], top;
bool viz1[N], viz2[N];
int nr_con;

void dfs1(int nod) {
  viz1[nod] = true;
  for (auto vec : nxt[nod])
    if (!viz1[vec])
      dfs1(vec);
  top.push_back(nod);
}

void dfs2(int nod) {
  viz2[nod] = true;
  con[nr_con].push_back(nod);
  for (auto vec : prv[nod])
    if (!viz2[vec])
      dfs2(vec);
}

int main() {
  ifstream cin("ctc.in");
  ofstream cout("ctc.out");
  int n, m;
  cin >> n >> m;
  while (m--) {
    int x, y;
    cin >> x >> y;
    nxt[x].push_back(y);
    prv[y].push_back(x);
  }
  cin.close();
  for (int i = 1; i <= n; ++i)
    if (!viz1[i])
      dfs1(i);
  reverse(top.begin(), top.end());
  for (auto i : top)
    if (!viz2[i]) {
      ++nr_con;
      dfs2(i);
    }
  cout << nr_con << "\n";
  for (int i = 1; i <= nr_con; ++i) {
    for (auto j: con[i])
      cout << j << " ";
    cout << "\n";
  }
  cout.close();
  return 0;
}