#include <bits/stdc++.h>
#define ll long long
#define all(a) (a).begin(), (a).end()
//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define fr first
#define sc second
#define pb push_back
#define er erase
#define in insert
#define pi pair<int,int>
#define pii pair<pair<int,int>,int>
#define mp make_pair
//#define int long long
#define rc(s) return cout<<s,0
#define rcc(s) cout<<s,exit(0)
using namespace std;

const int mod=1e9+7;
const int modp=1999999973;

int n,m,rs;
vector<int>nod1[100005],ans[100005];
vector<int>nod2[100005];
vector<int>parc;
bitset<100005>viz;

void DFS1(int s){
    viz[s]=1;
    parc.push_back(s);
    for(auto it:nod1[s]){
        if(viz[it]==0) DFS1(it);
    }
}


void DFS2(int s){
    ans[rs].push_back(s);
    viz[s]=1;
    for(auto it:nod2[s]) if(viz[it]==0) DFS2(it);
}

int32_t main(){
  //  ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
    ifstream fin("ctc.in");
  //  srand(chrono::steady_clock::now().time_since_epoch().count());
    ofstream fout("ctc.out");
    fin >> n >> m;
    for(int i=1;i<=m;i++){
        int x,y;
        fin >> x >> y;
        nod1[x].push_back(y);
        nod2[y].push_back(x);
    }
    for(int i=1;i<=n;i++){
        if(!viz[i]) DFS1(i);
    }
    viz.reset();
    for(int i=parc.size()-1;i>=0;i--){
        if(!viz[parc[i]]){
            rs++;
            DFS2(parc[i]);
        }
    }
    fout << rs << '\n';
    for(int i=1;i<=rs;i++){
        for(auto it:ans[i]) fout << it << ' ';
        fout << '\n';
    }
}