#include <bits/stdc++.h>
using namespace std;
/*
#include <atcoder/all>
using namespace atcoder;
*/
/*
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using bll = boost::multiprecision::cpp_int;
using bdouble = boost::multiprecision::number<boost::multiprecision::cpp_dec_float<100>>;
using namespace boost::multiprecision;
*/
#ifdef LOCAL_TEST
	#define BOOST_STACKTRACE_USE_ADDR2LINE
	#define BOOST_STACKTRACE_ADDR2LINE_LOCATION /usr/local/opt/binutils/bin/addr2line
	#define _GNU_SOURCE 1
	#include <boost/stacktrace.hpp>
	namespace std {
		template<typename T> class dvector : public std::vector<T> {
		public:
			dvector() : std::vector<T>() {}
			explicit dvector(size_t n, const T& value = T()) : std::vector<T>(n, value) {}
			dvector(const std::vector<T>& v) : std::vector<T>(v) {}
			dvector(const std::initializer_list<T> il) : std::vector<T>(il) {}
			dvector(const std::string::iterator first, const std::string::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::iterator first, const typename std::vector<T>::iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::reverse_iterator first, const typename std::vector<T>::reverse_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_iterator first, const typename std::vector<T>::const_iterator last) : std::vector<T>(first, last) {}
			dvector(const typename std::vector<T>::const_reverse_iterator first, const typename std::vector<T>::const_reverse_iterator last) : std::vector<T>(first, last) {}
			T& operator[](size_t n) {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
			const T& operator[](size_t n) const {
				try { return this->at(n); } catch (const std::exception& e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; return this->at(n); }
			}
		};
	}
	class dbool {
	private:
		bool boolvalue;
	public:
		dbool() : boolvalue(false) {}
		dbool(bool b) : boolvalue(b) {}
		operator bool&() { return boolvalue; }
		operator const bool&() const { return boolvalue; }
	};
	#define vector dvector
	#define bool dbool
	class SIGFPE_exception : std::exception {};
	class SIGSEGV_exception : std::exception {};
	void catch_SIGFPE([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGFPE_exception(); }
	void catch_SIGSEGV([[maybe_unused]] int e) { std::cerr << boost::stacktrace::stacktrace() << '\n'; throw SIGSEGV_exception(); }
	signed convertedmain();
	signed main() { signal(SIGFPE, catch_SIGFPE); signal(SIGSEGV, catch_SIGSEGV); return convertedmain(); }
	#define main() convertedmain()
#endif
#ifdef LOCAL_DEV
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::pair<T1, T2>& p) {
		return s << "(" << p.first << ", " << p.second << ")"; }
	template <typename T, size_t N> std::ostream& operator<<(std::ostream& s, const std::array<T, N>& a) {
		s << "{ "; for (size_t i = 0; i < N; ++i){ s << a[i] << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::set<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::multiset<T>& se) {
		s << "{ "; for (auto itr = se.begin(); itr != se.end(); ++itr){ s << (*itr) << "\t"; } s << "}"; return s; }
	template<typename T1, typename T2> std::ostream& operator<<(std::ostream& s, const std::map<T1, T2>& m) {
		s << "{\n"; for (auto itr = m.begin(); itr != m.end(); ++itr){ s << "\t" << (*itr).first << " : " << (*itr).second << "\n"; } s << "}"; return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::deque<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<T>& v) {
		for (size_t i = 0; i < v.size(); ++i){ s << v[i]; if (i < v.size() - 1) s << "\t"; } return s; }
	template<typename T> std::ostream& operator<<(std::ostream& s, const std::vector<std::vector<T>>& vv) {
		s << "\\\n"; for (size_t i = 0; i < vv.size(); ++i){ s << vv[i] << "\n"; } return s; }
	void debug_impl() { std::cerr << '\n'; }
	template<typename Head, typename... Tail> void debug_impl(Head head, Tail... tail) { std::cerr << " " << head << (sizeof...(tail) ? "," : ""); debug_impl(tail...); }
	#define debug(...) do { std::cerr << ":" << __LINE__ << " (" << #__VA_ARGS__ << ") ="; debug_impl(__VA_ARGS__); } while (false)
#else
	#define debug(...) do {} while (false)
#endif
//#define int long long
using ll = long long;
//constexpr int INF = (ll)1e9 + 7; //INT_MAX = (1<<31)-1 = 2147483647
constexpr ll INF = (ll)1e18; //(1LL<<63)-1 = 9223372036854775807
//constexpr ll MOD = (ll)1e9 + 7; //primitive root = 5
constexpr ll MOD = 998244353; //primitive root = 3
constexpr double EPS = 1e-9;
constexpr ll dx[4] = {1, 0, -1, 0};
constexpr ll dy[4] = {0, 1, 0, -1};
constexpr ll dx8[8] = {1, 0, -1, 0, 1, 1, -1, -1};
constexpr ll dy8[8] = {0, 1, 0, -1, 1, -1, 1, -1};
#define rep(i, n)   for(ll i=0, i##_length=(n); i< i##_length; ++i)
#define repeq(i, n) for(ll i=1, i##_length=(n); i<=i##_length; ++i)
#define rrep(i, n)   for(ll i=(n)-1; i>=0; --i)
#define rrepeq(i, n) for(ll i=(n)  ; i>=1; --i)
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
void p() { std::cout << '\n'; }
template<typename Head, typename... Tail> void p(Head head, Tail... tail) { std::cout << head << (sizeof...(tail) ? " " : ""); p(tail...); }
template<typename T> inline void pv(std::vector<T>& v) { for(ll i=0, N=v.size(); i<N; i++) std::cout << v[i] << " \n"[i==N-1]; }
template<typename T> inline bool chmax(T& a, T b) { return a < b && (a = b, true); }
template<typename T> inline bool chmin(T& a, T b) { return a > b && (a = b, true); }
template<typename T> inline void uniq(std::vector<T>& v) { v.erase(std::unique(v.begin(), v.end()), v.end()); }

/*-----8<-----template-----8<-----*/


class StronglyConnectedComponents {
public:
	const vector<vector<ll>> &g;
	vector<vector<ll>> gg, rg;
	vector< ll > comp, order, used;

	StronglyConnectedComponents(vector<vector<ll>> &g) : g(g), gg(g.size()), rg(g.size()), comp(g.size(), -1), used(g.size()) {
		for(ll i = 0; i < (ll)g.size(); i++) {
			for(ll e : g[i]) {
				gg[i].emplace_back(e);
				rg[e].emplace_back(i);
			}
		}
	}

	ll operator[](int k) {
		return comp[k];
	}

	void dfs(ll idx) {
		if(used[idx]) return;
		used[idx] = true;
		for(ll to : gg[idx]) dfs(to);
		order.push_back(idx);
	}

	void rdfs(ll idx, ll cnt) {
		if(comp[idx] != -1) return;
		comp[idx] = cnt;
		for(ll to : rg[idx]) rdfs(to, cnt);
	}

	void build(vector<vector<ll>> &t) {
		for(ll i = 0; i < (ll)gg.size(); i++) dfs(i);
		reverse(begin(order), end(order));
		ll ptr = 0;
		for(ll i : order) if(comp[i] == -1) rdfs(i, ptr), ptr++;

		t.resize(ptr);
		for(ll i = 0; i < (ll)g.size(); i++) {
			for(auto &to : g[i]) {
				ll x = comp[i], y = comp[to];
				if(x == y) continue;
				t[x].push_back(y);
			}
		}
	}
};

/*-----8<-----library-----8<-----*/

void solve() {
	ll N,M;
	cin>>N>>M;
	vector<vector<ll>> g(N);
	rep(i,M){
		ll a,b;
		cin>>a>>b;
		g[a].push_back(b);
	}
	debug(g);

	StronglyConnectedComponents scc(g);
	vector<vector<ll>> sccg;
	scc.build(sccg);
	debug(sccg);
	auto shrinkg = [](vector<vector<ll>> &g){
		for(ll i=0;i<(ll)g.size(); i++){
			g[i].erase(unique(g[i].begin(), g[i].end()), g[i].end());
		}
	};
	shrinkg(sccg);
	debug(sccg);

	vector<vector<ll>> v(sccg.size());
	rep(i,N){
		v[scc[i]].push_back(i);
	}
	p(sccg.size());
	rep(i,sccg.size()){
		cout<<v[i].size();
		for(ll x:v[i]){
			cout<<' '<<x;
		}
		cout<<'\n';
	}
}

signed main() {
	std::cin.tie(nullptr);
	std::ios::sync_with_stdio(false);
	//ll Q; cin >> Q; while(Q--)solve();
	solve();
	return 0;
}


Measured memory_bytes: 133328