#include <algorithm>
#include <iostream>
#include <fstream>
#include <climits>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <map>
#include <set>

#include <iomanip>
#include <cassert>

#include <random>
#include <chrono>

// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

using ull = unsigned long long;
using ll = long long;

//#define int __int128
#define int ll
#define pii pair <int, int>
#define all(a) (a).begin(), (a).end()
#define fr first
#define sc second
#define pb push_back
#define lb lower_bound
#define ub upper_bound

#define vt vector
#define FOR(a, b) for(int i = (a); i <= (b); i++)
#define FORr(a, b) for(int i = (a); i >= (b); i--)
#define sz(x) (int)(x).size()

#define YES cout << "YES\n"
#define NO cout << "NO\n"

using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int rangerng(int l, int r){
    return uniform_int_distribution<>(l, r)(rng);
}

string filename = "ctc";
ifstream fin(filename + ".in");
ofstream fout(filename + ".out");

////////////////////////////////////////////////////////////////////////////////////

const int NMAX = 1e5;

vt <int> adj[NMAX + 1];
vt <int> radj[NMAX + 1];

bool viz[NMAX + 1];
vt <int> topo;

void dfs(int node){
    viz[node] = 1;
    for(int vec : adj[node]){
        if(!viz[vec]){
            dfs(vec);
        }
    }
    topo.pb(node);
}

vt <vt <int>> comps;

vt <int> comp;
void dfs2(int node){
    viz[node] = 1;
    comp.pb(node);

    for(int vec : radj[node]){
        if(!viz[vec]){
            dfs2(vec);
        }
    }
}

void solve(){
    int n, m;
    fin >> n >> m;

    for(int i = 1; i <= m; i++){
        int a, b;
        fin >> a >> b;
        adj[a].pb(b);
        radj[b].pb(a);
    }

    for(int i = 1; i <= n; i++){
        if(!viz[i]){
            dfs(i);
        }
    }

    reverse(all(topo));

    for(int i = 1; i <= n; i++){
        viz[i] = 0;
    }

    for(int x : topo){
        if(!viz[x]){
            comp.clear();
            dfs2(x);
            comps.pb(comp);
        }
    }

    fout << sz(comps) << '\n';
    for(vt <int> x : comps){
        sort(all(x));
        for(int y : x){
            fout << y << ' ';
        }
        fout << '\n';
    }
}   


signed main(){

    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int T;
    //cin >> T;

    T = 1;

    while(T--){
        solve();
    }

    return 0;
}

/*
*/