#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define all(a) (a).begin(), (a).end()
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#define sz() size()
#define fr first
#define sc second
#define int long long
#define mp make_pair
#define rc(s) return cout<<s,0
#define rcc(s) cout<<s,exit(0)
using namespace std;

const int nmax = 100005;

int n,m,_curr = -1;
vector<int>nod[nmax],nod_R[nmax],vecc,scc[nmax];
bitset<nmax>viz;

void DFS(int s){
    viz[s] = 1;
    for(auto it : nod[s]){
        if(!viz[it]){
            DFS(it);
        }
    }
    vecc.push_back(s);
}

void DFS2(int s){
    viz[s] = 1;
    scc[_curr].push_back(s);
    for(auto it : nod_R[s]){
        if(!viz[it]){
            DFS2(it);
        }
    }
}

int32_t main(){
    ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
    srand(chrono::steady_clock::now().time_since_epoch().count());
    freopen("ctc.in","r",stdin);
    freopen("ctc.out","w",stdout);
    cin >> n >> m;
    for(int i=1;i<=m;i++){
        int x,y;
        cin >> x >> y;
        nod[x].push_back(y);
        nod_R[y].push_back(x);
    }
    for(int i=1;i<=n;i++){
        if(!viz[i]) DFS(i);
    }
    viz.reset();
    reverse(all(vecc));
    for(auto it : vecc){
        if(!viz[it]){
            ++_curr;
            DFS2(it);
        }
    }
    cout << (_curr + 1LL) << '\n';
    for(int i=0;i<=_curr;i++){
        for(auto it : scc[i]) cout << it << ' ';
        cout << '\n';
    }
}