#include <bits/stdc++.h>
using namespace std;
using i64 = long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  vector < vector < int > > es(n), res(n);
  for (int i = 0; i < m; i++) {
    int u, v;
    cin >> u >> v;
    es[u].push_back(v);
    res[v].push_back(u);
  }
  vector < int > d(n), b(n, -1), ord;
  auto dfs1 = [&](auto &self, int u, int dv) -> void {
    if (d[u]) return ;
    d[u] = dv;
    for (int v : es[u]) self(self, v, dv + 1);
    ord.push_back(u);
  };
  auto dfs2 = [&](auto &self, int u, int bv) -> void {
    if (~b[u]) return ;
    b[u] = bv;
    for (int v : res[u]) self(self, v, bv);
  };
  for (int i = 0; i < n; i++)
    if (!d[i]) dfs1(dfs1, i, 1);
  reverse(ord.begin(), ord.end());
  for (int i : ord)
    if (!~b[i]) dfs2(dfs2, i, i);
  vector < vector < int > > tans(n);
  for (int i = 0; i < n; i++) tans[b[i]].push_back(i);
  vector < vector < int > > ans;
  for (int i : ord)
    if (!tans[i].empty()) {
      ans.push_back({});
      for (int j : tans[i]) ans.back().push_back(j);
    }
  // reverse(ans.begin(), ans.end());
  cout << ans.size() << '\n';
  for (auto it : ans) {
    cout << it.size() << ' ';
    for (int i : it) cout << i << ' ';
    cout << '\n';
  }
  return 0;
}