#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,x,y,rs;
bitset<100005>viz;
vector<int>nod1[100005],nod2[100005],path,ans[100005];

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

void DFS2(int s){
    viz[s]=1;
    ans[rs].push_back(s);
    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);
    srand(chrono::steady_clock::now().time_since_epoch().count());
    ifstream fin("ctc.in");
    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]==0) DFS(i);
    }
    viz.reset();
    for(int i=path.size()-1;i>=0;i--){
        if(viz[path[i]]==0){
            rs++;
            DFS2(path[i]);
        }
    }
    fout << rs << '\n';
    for(int i=1;i<=rs;i++){
        for(auto it:ans[i]) fout << it << ' ';
        fout << '\n';
    }
}