// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define bit(n) (1LL<<(n))
#define F first
#define S second
// functions
template <typename T> void unique(T& c){c.erase(std::unique(c.begin(), c.end()), c.end());}
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 60;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

struct Graph{
  int n;
  vector<vector<int>> edge;
  vector<vector<int>> rev;
  vector<bool> used;
  vector<int> tn;
  vector<int> id;
  int cnt = 0;
  vector<vector<int>> scc_edge;
  Graph(){}
  Graph(int n): n(n){
    edge.resize(n);
    rev.resize(n);
    used.resize(n, false);
    id.resize(n);
  }
  void adde(int from, int to){
    edge[from].emplace_back(to);
    rev[to].emplace_back(from);
  }
  void dfs(int i){
    used[i] = true;
    for(auto e: edge[i]){
      if(!used[e])dfs(e);
    }
    tn.emplace_back(i);
  }
  void rev_dfs(int i, int cnt){
    used[i] = true;
    id[i] = cnt;
    for(auto e: rev[i]){
      if(!used[e]){
        rev_dfs(e, cnt);
      }
    }
  }
  int kosaraju(){
    tn.clear();
    fill(used.begin(), used.end(), false);

    for(int i = 0; i < n; i++){
      if(!used[i])dfs(i);
    }

    fill(used.begin(), used.end(), false);

    cnt = 0;
    for(int i = n - 1; i >= 0; i--){
      int v = tn[i];
      if(!used[v]){
        rev_dfs(v, cnt);
        cnt++;
      }
    }
    return cnt;
  }
  void compose(){
    scc_edge.resize(cnt);
    vector<set<int>> st(cnt);
    for(int i = 0; i < n; i++){
      for(auto e: edge[i]){
        if(id[e] != id[i] && st[id[i]].find(id[e]) == st[id[i]].end()){
          scc_edge[id[i]].emplace_back(id[e]);
          st[id[i]].insert(id[e]);
        }
      }
    }
  }
};

int main(int argc, char const* argv[])
{
  int n, m; cin >> n >> m;
  Graph g(n);
  rep(i, m){
    int a, b; cin >> a >> b;
    g.adde(a, b);
  }
  int r = g.kosaraju();
  cout << r << endl;
  vector<vector<int>> v(r);
  rep(i, n)v[g.id[i]].pb(i);
  rep(i, r)cout << sz(v[i]) << " " << v[i] << endl;
  return 0;
}


Measured memory_bytes: 79588