#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <stack>

#define pii pair <int, int>
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)x.size()
#define pb push_back
#define fr first
#define sc second
#define vt vector
#define ub upper_bound
#define lb lower_bound

using namespace std;

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];

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

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

int nrComp = 0;
vt <int> comp[NMAX + 1];

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

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

int main(){

    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]){
            ++nrComp;
            dfs2(x);
        }
    }

    fout << nrComp << '\n';
    for(int i = 1; i <= nrComp; i++){
        for(int x : comp[i]){
            fout << x << ' ';
        }
        fout << '\n';
    }

    return 0;
}