#line 2 "/Users/kaage/Desktop/ProgrammingWorkspace/library/other/template.hpp"
#define _CRT_SECURE_NO_WARNINGS
#pragma target("avx2")
#pragma optimize("O3")
#pragma optimize("unroll-loops")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <string.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define all(V) V.begin(),V.end()
typedef unsigned int uint;
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
typedef std::pair<lint, lint> LP;
constexpr int INF = INT_MAX/2;
constexpr lint LINF = LLONG_MAX/2;
constexpr double eps = DBL_EPSILON;
constexpr double PI=3.141592653589793238462643383279;
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
template <class T, class U>
inline bool chmax(T& lhs, const U& rhs) {
	if (lhs < rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
template <class T, class U>
inline bool chmin(T& lhs, const U& rhs) {
	if (lhs > rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
inline lint gcd(lint a, lint b) {
	while (b) {
		lint c = a;
		a = b; b = c % b;
	}
	return a;
}
inline lint lcm(lint a, lint b) {
	return a / gcd(a, b) * b;
}
bool isprime(lint n) {
	if (n == 1)return false;
	for (int i = 2; i * i <= n; i++) {
		if (n % i == 0)return false;
	}
	return true;
}
template<typename T>
T mypow(T a, lint b) {
	T res(1);
	while(b){
		if(b&1)res*=a;
		a*=a;
		b>>=1;
	}
	return res;
}
lint modpow(lint a, lint b, lint m) {
	lint res(1);
	while(b){
		if(b&1){
			res*=a;res%=m;
		}
		a*=a;a%=m;
		b>>=1;
	}
	return res;
}
template<typename T>
void printArray(std::vector<T>& vec) {
	rep(i, vec.size()){
		std::cout << vec[i];
		std::cout<<(i==(int)vec.size()-1?"\n":" ");
	}
}
template<typename T>
void printArray(T l, T r) {
	T rprev = std::prev(r);
	for (T i = l; i != rprev; i++) {
		std::cout << *i << " ";
	}
	std::cout << *rprev << std::endl;
}
LP extGcd(lint a,lint b) {
	if(b==0)return {1,0};
	LP s=extGcd(b,a%b);
	std::swap(s.first,s.second);
	s.second-=a/b*s.first;
	return s;
}
LP ChineseRem(const lint& b1,const lint& m1,const lint& b2,const lint& m2) {
	lint p=extGcd(m1,m2).first;
	lint tmp=(b2-b1)*p%m2;
	lint r=(b1+m1*tmp+m1*m2)%(m1*m2);
	return std::make_pair(r,m1*m2);
}
template<typename F>
inline constexpr decltype(auto) lambda_fix(F&& f){
	return [f=std::forward<F>(f)](auto&&... args){
		return f(f,std::forward<decltype(args)>(args)...);
	};
}
#line 3 "/Users/kaage/Desktop/ProgrammingWorkspace/library/graph/StronglyConnectedComponents.hpp"
class StronglyConnectedComponents{
	int N;
	std::vector<std::vector<int>> vec,rvec;
public:
	StronglyConnectedComponents(int N):N(N){
		vec.resize(N);rvec.resize(N);
	}
	void add_edge(int from,int to){
		vec[from].emplace_back(to);
		rvec[to].emplace_back(from);
	}
	std::vector<std::vector<int>> get_scc(){
		std::vector<bool> used(N);
		std::vector<int> vs;
		std::vector<std::vector<int>> res;
		auto dfs=lambda_fix([&](auto self,int node)->void{
			used[node]=true;
			for(const int& i:vec[node]){
				if(!used[i])self(self,i);
			}
			vs.emplace_back(node);
		});
		auto rdfs=lambda_fix([&](auto self,int node)->void{
			used[node]=true;
			res.back().emplace_back(node);
			for(const int& i:rvec[node]){
				if(!used[i])self(self,i);
			}
		});
		rep(i,N){
			if(!used[i])dfs(i);
		}
		used.assign(N,false);
		for(int i=N-1;i>=0;i--){
			if(!used[vs[i]]){
				res.emplace_back();
				rdfs(vs[i]);
			}
		}
		return res;
	}
};
#line 3 "main.cpp"
int N,M;
int main(){
	scanf("%d%d",&N,&M);
	StronglyConnectedComponents scc(N);
	rep(i,M){
		int a,b;
		scanf("%d%d",&a,&b);
		scc.add_edge(a,b);
	}
	auto vec=scc.get_scc();
	printf("%d\n",vec.size());
	rep(i,vec.size()){
		printf("%d ",vec[i].size());
		printArray(vec[i]);
	}
	return 0;
}

Measured memory_bytes: 75968