#define LOCAL
#define _USE_MATH_DEFINES
#include <array>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
#include <complex>
#include <cmath>
#include <numeric>
#include <bitset>
#include <functional>
#include <random>
#include <ctime>

using namespace std;

template <typename A, typename B>
ostream& operator <<(ostream& out, const pair<A, B>& a) {
  out << "(" << a.first << "," << a.second << ")";
  return out;
}
template <typename T, size_t N>
ostream& operator <<(ostream& out, const array<T, N>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T>
ostream& operator <<(ostream& out, const vector<T>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T, class Cmp>
ostream& operator <<(ostream& out, const set<T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
  return out;
}
template <typename U, typename T, class Cmp>
ostream& operator <<(ostream& out, const map<U, T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& p : a) { out << (first ? "" : ", "); out << p.first << ":" << p.second; first = 0;} out << "}";
  return out;
}
#ifdef LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 42
#endif
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
  cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << ": " << arg1 << " |";
  __f(comma + 1, args...);
}

typedef long long int64;
typedef pair<int, int> ii;
#define SZ(x) (int)((x).size())
const int INF = 1 << 29;
const int MOD = 1e9 + 7;
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }

struct fast_ios {
  fast_ios() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
  };
} fast_ios_;

int main() {
  int n, m;
  cin >> n >> m;
  vector<vector<int>> a(n);
  for (int i = 0; i < m; ++i) {
    int x, y;
    cin >> x >> y;
    a[x].push_back(y);
  }

  vector<int> dfn(n), low(n), scc(n), S, ret;
  vector<bool> instack(n);
  int stamp = 1;
  function<void(int)> DFS =
    [&](int u) -> void {
      low[u] = dfn[u] = stamp++;
      S.push_back(u);
      instack[u] = true;
      for (auto& v : a[u]) {
        if (dfn[v] == 0) {
          DFS(v);
          low[u] = min(low[u], low[v]);
        } else if (instack[v]) {
          low[u] = min(low[u], dfn[v]);
        }
      }
      if (low[u] == dfn[u]) {
        while (true) {
          int v = S.back();
          scc[v] = u;
          ret.push_back(v);
          instack[v] = false;
          S.pop_back();
          if (v == u) break;
        }
      }
    };
  for (int i = 0; i < n; ++i) {
    if (!dfn[i]) DFS(i);
  }
  reverse(ret.begin(), ret.end());
  vector<vector<int>> ans;
  for (int i = 0, j; i < n; i = j) {
    vector<int> cur;
    for (j = i; j < n && scc[ret[j]] == scc[ret[i]]; ++j) cur.push_back(ret[j]);
    ans.push_back(cur);
  }
  cout << SZ(ans) << '\n';
  for (auto& v : ans) {
    cout << SZ(v);
    for (auto& x : v) {
      cout << " " << x;
    }
    cout << '\n';
  }
  return 0;
}


Measured memory_bytes: 61820