This documentation is automatically generated by online-judge-tools/verification-helper
#define PROBLEM "https://judge.yosupo.jp/problem/scc"
#include "Template/template.hpp"
#include "Graph/scc.hpp"
int main(){
int n,m;
cin>>n>>m;
SCC scc(n);
rep(i,0,m){
int x,y;
cin>>x>>y;
scc.add_edge(x,y);
}
scc.run();
vector g(scc.m,vector<int>());
rep(i,0,n)g[scc.id[i]].push_back(i);
cout<<g.size()<<'\n';
rep(i,0,g.size()){
cout<<g[i].size()<<' ';
rep(j,0,g[i].size())cout<<g[i][j]<<(j==(int)g[i].size()-1?'\n':' ');
}
return 0;
}
#line 1 "Verify/LC_scc.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/scc"
#line 1 "Template/template.hpp"
#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rrep(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); i--)
#define ALL(v) (v).begin(), (v).end()
#define UNIQUE(v) sort(ALL(v)), (v).erase(unique(ALL(v)), (v).end())
#define SZ(v) (int)v.size()
#define MIN(v) *min_element(ALL(v))
#define MAX(v) *max_element(ALL(v))
#define LB(v, x) int(lower_bound(ALL(v), (x)) - (v).begin())
#define UB(v, x) int(upper_bound(ALL(v), (x)) - (v).begin())
using uint = unsigned int;
using ll = long long int;
using ull = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;
const int inf = 0x3fffffff;
const ll INF = 0x1fffffffffffffff;
template <typename T, typename S = T> S SUM(const vector<T> &a) {
return accumulate(ALL(a), S(0));
}
template <typename S, typename T = S> S POW(S a, T b) {
S ret = 1, base = a;
for (;;) {
if (b & 1)
ret *= base;
b >>= 1;
if (b == 0)
break;
base *= base;
}
return ret;
}
template <typename T> inline bool chmax(T &a, T b) {
if (a < b) {
a = b;
return 1;
}
return 0;
}
template <typename T> inline bool chmin(T &a, T b) {
if (a > b) {
a = b;
return 1;
}
return 0;
}
template <typename T, typename U> T ceil(T x, U y) {
assert(y != 0);
if (y < 0)
x = -x, y = -y;
return (x > 0 ? (x + y - 1) / y : x / y);
}
template <typename T, typename U> T floor(T x, U y) {
assert(y != 0);
if (y < 0)
x = -x, y = -y;
return (x > 0 ? x / y : (x - y + 1) / y);
}
template <typename T> int popcnt(T x) {
return __builtin_popcountll(x);
}
template <typename T> int topbit(T x) {
return (x == 0 ? -1 : 63 - __builtin_clzll(x));
}
template <typename T> int lowbit(T x) {
return (x == 0 ? -1 : __builtin_ctzll(x));
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
os << "P(" << p.first << ", " << p.second << ")";
return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
os << "{";
for (int i = 0; i < vec.size(); i++) {
os << vec[i] << (i + 1 == vec.size() ? "" : ", ");
}
os << "}";
return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &map_var) {
os << "{";
for (auto itr = map_var.begin(); itr != map_var.end(); itr++) {
os << "(" << itr->first << ", " << itr->second << ")";
itr++;
if (itr != map_var.end())
os << ", ";
itr--;
}
os << "}";
return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &set_var) {
os << "{";
for (auto itr = set_var.begin(); itr != set_var.end(); itr++) {
os << *itr;
++itr;
if (itr != set_var.end())
os << ", ";
itr--;
}
os << "}";
return os;
}
#ifdef LOCAL
#define debug 1
#define show(...) _show(0, #__VA_ARGS__, __VA_ARGS__)
#else
#define debug 0
#define show(...) true
#endif
template <typename T> void _show(int i, T name) {
cerr << '\n';
}
template <typename T1, typename T2, typename... T3>
void _show(int i, const T1 &a, const T2 &b, const T3 &...c) {
for (; a[i] != ',' && a[i] != '\0'; i++)
cerr << a[i];
cerr << ":" << b << " ";
_show(i + 1, a, c...);
}
#line 2 "Graph/scc.hpp"
struct SCC{
int n,m,cur;
vector<vector<int>> g;
vector<int> low,ord,id;
SCC(int _n=0):n(_n),m(0),cur(0),g(_n),low(_n),ord(_n,-1),id(_n){}
void resize(int _n){
n=_n;
g.resize(n);
low.resize(n);
ord.resize(n,-1);
id.resize(n);
}
void add_edge(int u,int v){g[u].emplace_back(v);}
void dfs(int v,vector<int>& used){
ord[v]=low[v]=cur++;
used.emplace_back(v);
for(auto& nxt:g[v]){
if(ord[nxt]==-1){
dfs(nxt,used); chmin(low[v],low[nxt]);
}
else{
chmin(low[v],ord[nxt]);
}
}
if(ord[v]==low[v]){
while(1){
int add=used.back(); used.pop_back();
ord[add]=n; id[add]=m;
if(v==add)break;
}
m++;
}
}
void run(){
vector<int> used;
rep(v,0,n)if(ord[v]==-1)dfs(v,used);
for(auto& x:id)x=m-1-x;
}
};
/**
* @brief Strongly Connected Components
*/
#line 5 "Verify/LC_scc.test.cpp"
int main(){
int n,m;
cin>>n>>m;
SCC scc(n);
rep(i,0,m){
int x,y;
cin>>x>>y;
scc.add_edge(x,y);
}
scc.run();
vector g(scc.m,vector<int>());
rep(i,0,n)g[scc.id[i]].push_back(i);
cout<<g.size()<<'\n';
rep(i,0,g.size()){
cout<<g[i].size()<<' ';
rep(j,0,g[i].size())cout<<g[i][j]<<(j==(int)g[i].size()-1?'\n':' ');
}
return 0;
}