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

using namespace std;

#define pii pair <int, int>

string filename = "ctc";

#ifdef LOCAL
    ifstream fin("input.in");
    ofstream fout("output.out");
#else
    ifstream fin(filename + ".in");
    ofstream fout(filename + ".out");
#endif

const int NMAX = 1e5;

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

bool viz[NMAX + 1];

vector <int> topo;
void dfs(int node){
    viz[node] = true;
    for(int vec : adj[node]){
        if(!viz[vec]){
            dfs(vec);
        }
    }
    topo.push_back(node);
}

vector <int> aux;
void dfs2(int node){
    viz[node] = true;
    aux.push_back(node);
    for(int vec : radj[node]){
        if(!viz[vec]){
            dfs2(vec);
        }
    }
}

vector <vector <int>> comps;

int main(){

    int n, m;
    fin >> n >> m;

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

    for(int i = 1; i <= n; i++){
        if(!viz[i]){
            dfs(i);
        }
    }
    reverse(topo.begin(), topo.end());

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

    for(int node : topo){
        if(!viz[node]){
            aux.clear();
            dfs2(node);
            comps.push_back(aux);
        }
    }

    fout << (int)comps.size() << '\n';
    for(vector <int> comp : comps){
        for(int node : comp){
            fout << node << ' ';
        }
        fout << '\n';
    }

    return 0;
}