/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author aajisaka
 */


#include<bits/stdc++.h>

using namespace std;

void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

#define SPEED ios_base::sync_with_stdio(false);cin.tie(nullptr)
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

using ll = long long;
using ull = unsigned long long;
using P = pair<ll, ll>;

constexpr long double PI = 3.14159265358979323846264338327950288L;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());


#include <algorithm>
#include <cassert>
#include <vector>



#include <utility>


namespace internal {

    template <class E> struct csr {
        std::vector<int> start;
        std::vector<E> elist;
        csr(int n, const std::vector<std::pair<int, E>>& edges)
            : start(n + 1), elist(edges.size()) {
          for (auto e : edges) {
            start[e.first + 1]++;
          }
          for (int i = 1; i <= n; i++) {
            start[i] += start[i - 1];
          }
          auto counter = start;
          for (auto e : edges) {
            elist[counter[e.first]++] = e.second;
          }
        }
    };

// Reference:
// R. Tarjan,
// Depth-First Search and Linear Graph Algorithms
    struct scc_graph {
    public:
        scc_graph(int n) : _n(n) {}

        int num_vertices() { return _n; }

        void add_edge(int from, int to) { edges.push_back({from, {to}}); }

        // @return pair of (# of scc, scc id)
        std::pair<int, std::vector<int>> scc_ids() {
          auto g = csr<edge>(_n, edges);
          int now_ord = 0, group_num = 0;
          std::vector<int> visited, low(_n), ord(_n, -1), ids(_n);
          visited.reserve(_n);
          auto dfs = [&](auto self, int v) -> void {
              low[v] = ord[v] = now_ord++;
              visited.push_back(v);
              for (int i = g.start[v]; i < g.start[v + 1]; i++) {
                auto to = g.elist[i].to;
                if (ord[to] == -1) {
                  self(self, to);
                  low[v] = std::min(low[v], low[to]);
                } else {
                  low[v] = std::min(low[v], ord[to]);
                }
              }
              if (low[v] == ord[v]) {
                while (true) {
                  int u = visited.back();
                  visited.pop_back();
                  ord[u] = _n;
                  ids[u] = group_num;
                  if (u == v) break;
                }
                group_num++;
              }
          };
          for (int i = 0; i < _n; i++) {
            if (ord[i] == -1) dfs(dfs, i);
          }
          for (auto& x : ids) {
            x = group_num - 1 - x;
          }
          return {group_num, ids};
        }

        std::vector<std::vector<int>> scc() {
          auto ids = scc_ids();
          int group_num = ids.first;
          std::vector<int> counts(group_num);
          for (auto x : ids.second) counts[x]++;
          std::vector<std::vector<int>> groups(ids.first);
          for (int i = 0; i < group_num; i++) {
            groups[i].reserve(counts[i]);
          }
          for (int i = 0; i < _n; i++) {
            groups[ids.second[i]].push_back(i);
          }
          return groups;
        }

    private:
        int _n;
        struct edge {
            int to;
        };
        std::vector<std::pair<int, edge>> edges;
    };

}  // namespace internal

struct scc_graph {
public:
    scc_graph() : internal(0) {}
    scc_graph(int n) : internal(n) {}

    void add_edge(int from, int to) {
      int n = internal.num_vertices();
      assert(0 <= from && from < n);
      assert(0 <= to && to < n);
      internal.add_edge(from, to);
    }

    std::vector<std::vector<int>> scc() { return internal.scc(); }

private:
    internal::scc_graph internal;
};


class GSCC {
public:
    void solve(istream& cin, ostream& cout) {
      SPEED;
      int n, m; cin >> n >> m;
      auto scc = scc_graph(n);
      rep(i, m) {
        int a, b; cin >> a >> b;
        scc.add_edge(a, b);
      }
      auto ret = scc.scc();
      cout << ret.size() << '\n';
      for(auto& v: ret) {
        cout << v.size() << ' ';
        for(auto& e: v) {
          cout << e << ' ';
        }
        cout << '\n';
      }
    }
};

signed main() {
  GSCC solver;
  std::istream& in(std::cin);
  std::ostream& out(std::cout);
  solver.solve(in, out);
  return 0;
}

Measured memory_bytes: 40560