#include <bits/stdc++.h>

#ifdef DEBUG
#include <Mylib/Debug/debug.cpp>
#else
#define dump(...) ((void)0)
#endif

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

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

template <typename T, size_t N, typename U>
void fill_array(T (&a)[N], const U &v){
  std::fill((U*)a, (U*)(a + N), v);
}

template <typename T, size_t N, size_t I = N>
auto make_vector(const std::array<int, N> &a, T value = T()){
  static_assert(I >= 1);
  static_assert(N >= 1);
  if constexpr (I == 1){
    return std::vector<T>(a[N - I], value);
  }else{
    return std::vector(a[N - I], make_vector<T, N, I - 1>(a, value));
  }
}

template <typename T>
std::ostream& operator<<(std::ostream &s, const std::vector<T> &a){
  for(auto it = a.begin(); it != a.end(); ++it){
    if(it != a.begin()) s << " ";
    s << *it;
  }
  return s;
}

template <typename T>
std::istream& operator>>(std::istream &s, std::vector<T> &a){
  for(auto &x : a) s >> x;
  return s;
}

namespace haar_lib {
  template <typename T>
  struct edge {
    int from, to;
    T cost;
    int index = -1;
    edge(){}
    edge(int from, int to, T cost): from(from), to(to), cost(cost){}
    edge(int from, int to, T cost, int index): from(from), to(to), cost(cost), index(index){}
  };

  template <typename T>
  struct graph {
    using weight_type = T;
    using edge_type = edge<T>;

    std::vector<std::vector<edge<T>>> data;

    auto& operator[](size_t i){return data[i];}
    const auto& operator[](size_t i) const {return data[i];}

    auto begin() const {return data.begin();}
    auto end() const {return data.end();}

    graph(){}
    graph(int N): data(N){}

    bool empty() const {return data.empty();}
    int size() const {return data.size();}

    void add_edge(int i, int j, T w, int index = -1){
      data[i].emplace_back(i, j, w, index);
    }

    void add_undirected(int i, int j, T w, int index = -1){
      add_edge(i, j, w, index);
      add_edge(j, i, w, index);
    }

    template <size_t I, bool DIRECTED = true, bool WEIGHTED = true>
    void read(int M){
      for(int i = 0; i < M; ++i){
        int u, v; std::cin >> u >> v;
        u -= I;
        v -= I;
        T w = 1;
        if(WEIGHTED) std::cin >> w;
        if(DIRECTED) add_edge(u, v, w, i);
        else add_undirected(u, v, w, i);
      }
    }
  };

  template <typename T>
  using tree = graph<T>;
}

namespace haar_lib {
  template <typename T>
  std::optional<std::vector<int>> topological_sort(const graph<T> &g){
    const int n = g.size();
    std::vector<int> indeg(n);

    for(int i = 0; i < n; ++i){
      for(auto &e : g[i]){
        ++indeg[e.to];
      }
    }

    std::queue<int> q;
    for(int i = 0; i < n; ++i){
      if(indeg[i] == 0) q.push(i);
    }

    std::vector<int> ret;
    while(not q.empty()){
      int cur = q.front(); q.pop();
      ret.push_back(cur);
      for(auto &e : g[cur]){
        --indeg[e.to];
        if(indeg[e.to] == 0){
          q.push(e.to);
        }
      }
    }

    if((int)ret.size() == n){
      return {ret};
    }else{
      return std::nullopt;
    }
  }
}



namespace haar_lib {
  template <typename T>
  auto strongly_connected_components(const graph<T> &g){
    const int n = g.size();

    std::vector<int> ret(n), low(n, -1), ord(n, -1), S;
    std::vector<bool> check(n);
    S.reserve(n);
    int t = 0;
    int k = 0;

    auto dfs =
      [&](auto &dfs, int cur) -> void {
        low[cur] = ord[cur] = t++;
        S.push_back(cur);
        check[cur] = true;

        for(auto &e : g[cur]){
          if(ord[e.to] == -1){
            dfs(dfs, e.to);
            low[cur] = std::min(low[cur], low[e.to]);
          }else if(check[e.to]){
            low[cur] = std::min(low[cur], low[e.to]);
          }
        }

        if(low[cur] == ord[cur]){
          while(true){
            int u = S.back(); S.pop_back();
            check[u] = false;
            ret[u] = k;
            if(cur == u) break;
          }
          ++k;
        }
      };

    for(int i = 0; i < n; ++i){
      if(ord[i] == -1){
        t = 0;
        dfs(dfs, i);
      }
    }

    for(auto &x : ret) x = k - 1 - x;

    return std::make_pair(ret, k);
  }
}



namespace solver {
  namespace hl = haar_lib;

  void init(){
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed << std::setprecision(12);
    std::cerr << std::fixed << std::setprecision(12);
    std::cin.exceptions(std::ios_base::failbit);
  }

  void solve(){
    int N, M; std::cin >> N >> M;

    hl::graph<int> g(N);
    g.read<0, true, false>(M);

    auto [scc, K] = hl::strongly_connected_components(g);

    std::vector<std::vector<int>> ans(K);
    for(int i = 0; i < N; ++i) ans[scc[i]].push_back(i);

    // hl::graph<int> g2(K);
    // for(auto &v : g){
    //   for(auto &e : v){
    //     if(scc[e.from] != scc[e.to]) g2.add_edge(scc[e.from], scc[e.to], 1);
    //   }
    // }

    // auto ts = hl::topological_sort(std::move(g2)).value();

    std::cout << K << "\n";

    for(int i = 0; i < K; ++i){

    //    for(auto i : ts){
      auto &t = ans[i];
      std::cout << t.size() << " " << t << "\n";
    }
  }
}

int main(){
  solver::init();
  while(true){
    try{
      solver::solve();
    }catch(const std::istream::failure &e){
      break;
    }
  }
  return 0;
}


Measured memory_bytes: 59320