Kosaraju

#define NguyenDangQuan the_author
#define my_heart love_you_to_the_moon_and_back

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;

const int N = 2e5 + 5;
int n, m;
vector<int> adj[N], nadj[N], s;
int lt[N], l = 0;

void Read(){
    cin >> n >> m;
    while(m--){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        nadj[v].push_back(u);
    }
}

void dfs(int v){
    lt[v] = 1;
    for(auto i : adj[v])
        if(!lt[i])
            dfs(i);
    s.push_back(v);
}

void dfs_component(int v){
    lt[v] = l;
    cout << v << " ";
    for(auto i : nadj[v])
        if(!lt[i])
            dfs_component(i);
}

void Kosaraju(){
    for(int i = 1; i <= n; ++i)
        if(lt[i] == 0)
            dfs(i);
    for(int i = 1; i <= n; ++i)
        lt[i] = 0;
    while(s.size()){
        int c = s.back();
        s.pop_back();
        if(lt[c] != 0)
            continue;
        ++l;
        dfs_component(c);
        cout << "\n";
    }
}

void Solve(){
    Kosaraju();
    cout << l;
}

main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    Read();
    Solve();
}