#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int nmax=50000;
vector <int> g[nmax+5],gt[nmax+5];
vector <int> ctc[nmax+5];
int n,m,use[nmax+5],nrctc;
void read(){
    fin>>n>>m;
    for(int i=1;i<=m;++i){
        int x,y;
        fin>>x>>y;
        g[x].push_back(y);
        gt[y].push_back(x);
    }
}
void dfsp(int nod){
    use[nod]=1;
    for(auto vecin:g[nod])
        if(!use[vecin])
            dfsp(vecin);
}
void dfsm(int nod){
    use[nod]=2;
    ctc[nrctc].push_back(nod);
    //fout<<nod<<" ";
    for(auto vecin:gt[nod])
        if(use[vecin]==1)
            dfsm(vecin);
}
void print(){
    fout<<nrctc<<"\n";
    for(int i=1;i<=nrctc;++i){
        for(auto nod:ctc[i])
            fout<<nod<<" ";
        fout<<"\n";
    }
}
int main()
{
    read();
    for(int i=1;i<=n;++i){
        if(use[i]==0){
            nrctc++;
            dfsp(i);
            dfsm(i);
            //fout<<endl;
            for(int i=1;i<=n;++i)
                if(use[i]==1)
                    use[i]=0;
        }
    }
    print();
    return 0;
}