#include <bits/stdc++.h>

#include <boost/hana/functional/fix.hpp>

template <typename T, typename = void>
struct is_iterable : std::false_type {};
template <typename T>
struct is_iterable<T, std::void_t<decltype(std::begin(std::declval<T>())),
                                  decltype(std::end(std::declval<T>()))>>
    : std::true_type {};

template <typename T, typename = void>
struct is_pair : std::false_type {};
template <typename T>
struct is_pair<T, std::void_t<decltype(std::declval<T>().first),
                              decltype(std::declval<T>().second)>>
    : std::true_type {};

template <typename T>
void debug(const T& v) {
  if constexpr (is_pair<T>::value) {
    std::cerr << "{";
    debug(v.first);
    std::cerr << ", ";
    debug(v.second);
    std::cerr << "}";
  } else if constexpr (is_iterable<T>::value &&
                       !std::is_same<T, std::string>::value) {
    std::cerr << "{";
    for (auto it = std::begin(v); it != std::end(v); ++it) {
      if (it != std::begin(v)) std::cerr << ", ";
      debug(*it);
    }
    std::cerr << "}";
  } else {
    std::cerr << v;
  }
}
template <typename T, typename... Ts>
void debug(const T& value, const Ts&... args) {
  debug(value);
  std::cerr << ", ";
  debug(args...);
}
#if DEBUG
#define dbg(...)                        \
  do {                                  \
    cerr << #__VA_ARGS__ << ": ";       \
    debug(__VA_ARGS__);                 \
    cerr << " (L" << __LINE__ << ")\n"; \
  } while (0)
#else
#define dbg(...)
#endif

void read_from_cin() {}
template <typename T, typename... Ts>
void read_from_cin(T& value, Ts&... args) {
  std::cin >> value;
  read_from_cin(args...);
}
#define rd(type, ...) \
  type __VA_ARGS__;   \
  read_from_cin(__VA_ARGS__);
#define ints(...) rd(int, __VA_ARGS__);
#define strings(...) rd(string, __VA_ARGS__);

template <typename T>
void write_to_cout(const T& value) {
  if constexpr (std::is_same<T, bool>::value) {
    std::cout << (value ? "Yes" : "No");
  } else {
    std::cout << value;
  }
}
template <typename T, typename... Ts>
void write_to_cout(const T& value, const Ts&... args) {
  write_to_cout(value);
  std::cout << ' ';
  write_to_cout(args...);
}
#define wt(...)                 \
  do {                          \
    write_to_cout(__VA_ARGS__); \
    cout << '\n';               \
  } while (0)

#define all(x) (x).begin(), (x).end()

#define rep_dispatch(_1, _2, _3, name, ...) name

#define rep3(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep2(i, n) rep3(i, 0, n)
#define rep1(n) rep2(_loop_variable_, n)
#define rep(...) rep_dispatch(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep3(i, a, b) for (int i = (int)(b)-1; i >= a; --i)
#define rrep2(i, n) rrep3(i, 0, n)
#define rrep1(n) rrep2(_loop_variable_, n)
#define rrep(...) rep_dispatch(__VA_ARGS__, rrep3, rrep2, rrep1)(__VA_ARGS__)

template <typename T>
std::istream& operator>>(std::istream& is, std::vector<T>& v) {
  for (T& vi : v) is >> vi;
  return is;
}

template <typename T, typename U>
std::istream& operator>>(std::istream& is, std::pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T, typename U>
bool chmax(T& a, U b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T, typename U>
bool chmin(T& a, U b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

template <typename T, typename U>
T max(T a, U b) {
  return a > b ? a : b;
}

template <typename T, typename U>
T mix(T a, U b) {
  return a < b ? a : b;
}

template <typename T>
int sz(const T& v) {
  return v.size();
}

template <typename T>
int popcount(T i) {
  return std::bitset<std::numeric_limits<T>::digits>(i).count();
}

using i64 = std::int64_t;
using i32 = std::int32_t;

template <typename T>
using low_priority_queue =
    std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <typename T>
using V = std::vector<T>;
template <typename T>
using VV = V<V<T>>;

void Main();

int main() {
  Main();
  return 0;
}

const auto& Fix = boost::hana::fix;

using namespace std;

#define int i64

struct FastIO {
  FastIO() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);
  }
} fast_io;
#pragma once

template <typename T>
struct Edge {
  int from, to;
  T weight;
};

template <typename T>
class Graph {
 public:
  Graph(int n) : edges_(n) {}
  void AddEdge(int from, int to, T weight = T()) {
    edges_[from].push_back({from, to, weight});
  }
  const std::vector<Edge<T>>& Edges(int from) const { return edges_[from]; }
  int NumVertices() const { return edges_.size(); }

 private:
  std::vector<std::vector<Edge<T>>> edges_;
};

template <typename T>
std::vector<std::vector<int>> StronglyConnectedComponents(
    const Graph<T>& graph) {
  int n = graph.NumVertices();
  std::vector<int> nodes;
  std::vector<bool> visited(n);
  std::function<void(int)> dfs = [&](int u) {
    visited[u] = true;
    for (const Edge<T>& e : graph.Edges(u)) {
      if (!visited[e.to]) {
        dfs(e.to);
      }
    }
    nodes.push_back(u);
  };
  for (int u = 0; u < n; ++u) {
    if (!visited[u]) dfs(u);
  }
  std::vector<std::vector<int>> rgraph(n);
  for (int u = 0; u < n; ++u) {
    for (const Edge<T> e : graph.Edges(u)) {
      rgraph[e.to].push_back(u);
    }
  }
  std::vector<bool> rvisited(n);
  std::vector<std::vector<int>> sccs;
  std::function<void(std::vector<int>&, int)> rdfs = [&](std::vector<int>& scc,
                                                         int u) {
    rvisited[u] = true;
    scc.push_back(u);
    for (int v : rgraph[u]) {
      if (!rvisited[v]) {
        rdfs(scc, v);
      }
    }
  };
  for (int i = n - 1; i >= 0; --i) {
    int u = nodes[i];
    if (!rvisited[u]) {
      std::vector<int> scc;
      rdfs(scc, u);
      sccs.push_back(scc);
    }
  }
  return sccs;
}

template <typename T>
std::vector<int> TopologicalSort(const Graph<T>& graph) {
  const int n = graph.NumVertices();
  std::vector<bool> permanent(n), temporary(n);
  std::vector<int> ret;
  std::function<void(int)> visit = [&](int n) {
    if (permanent[n]) return;
    assert(!temporary[n]);
    temporary[n] = true;
    for (const auto& e : graph.Edges(n)) visit(e.to);
    temporary[n] = false;
    permanent[n] = true;
    ret.push_back(n);
  };
  for (int i = 0; i < n; ++i) {
    if (!permanent[i]) visit(i);
  }
  reverse(ret.begin(), ret.end());
  return ret;
}

void Main() {
  ints(n, m);
  Graph<int> g(n);
  rep(m) {
    ints(a, b);
    g.AddEdge(a, b);
  }

  VV<int> scc = StronglyConnectedComponents(g);
  V<int> scc_index(n);
  rep(i, scc.size()) for (int u : scc[i]) scc_index[u] = i;

  wt(scc.size());
  for (const auto& scci : scc) {
    cout << scci.size();
    for (int j : scci) cout << " " << j;
    cout << endl;
  }
}


Measured memory_bytes: 84712