#include<fstream>
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
vector<vector<int>>graph;
vector<vector<int>>revGraph;
vector<int>sortTop;
vector<bool>viz;
int pozCrt;
int n,m;
void DFSTop(int &nodCrt){
    viz[nodCrt]=1;
    for(auto i:graph[nodCrt]){
        if(!viz[i]){
            DFSTop(i);
        }
    }
    sortTop[pozCrt]=nodCrt;
    --pozCrt;
}
void getSortTop(){
    pozCrt=n-1;
    sortTop.resize(n);
    for(int i=1;i<=n;++i){
        if(!viz[i]){
            DFSTop(i);
        }
    }
}
vector<vector<int>>componenteConexe;
void DFSAnswer(int &nodCrt){
    viz[nodCrt]=1;
    for(auto i:revGraph[nodCrt]){
        if(!viz[i]){
            DFSAnswer(i);
        }
    }
    componenteConexe.back().push_back(nodCrt);
}

int main(){
    fin>>n>>m;
    graph.resize(n+1);
    revGraph.resize(n+1);
    viz.resize(n+1);
    int u,v;
    for(int i=0;i<m;++i){
        fin>>u>>v;
        graph[u].push_back(v);
        revGraph[v].push_back(u);
    }
    getSortTop();
    fill(viz.begin(),viz.end(),false);
    for(int i=0;i<n;++i){
        if(!viz[sortTop[i]]){
            componenteConexe.push_back({});
            DFSAnswer(sortTop[i]);
        }
    }
    fout<<componenteConexe.size()<<"\n";
    for(int i=0;i<componenteConexe.size();++i){
        for(int j=0;j<componenteConexe[i].size();++j){
            fout<<componenteConexe[i][j]<<" ";
        }
        fout<<"\n";
    }
    return 0;
}