#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

    ifstream fin("ctc.in");
    ofstream fout("ctc.out");

vector <int> G[100000];
vector <int> Gi[100000];
vector <int> Go[100000];
vector <int> used;
vector <int> where;
vector <int> discovered;

void DFP(const int n ,vector <int> *G)
{
    vector<int>::iterator it;
    used[n]=true;

    for(it=G[n].begin();it!=G[n].end();it++)
        if(used[*it]==false)
            DFP(*it,G);

    discovered.push_back(n);
}

void DFM(const int n ,const int which, vector <int> *G)
{
    vector<int>::iterator it;
    where[n]=which;

    for(it=G[n].begin();it!=G[n].end();it++)
        if(where[*it]==-1)
            DFM(*it,which,G);
}

int main()
{
    int n,m,x,y;

    fin>>n>>m;

    for(int i=1; i<=m; i++){
          fin>>x>>y;
          Go[x-1].push_back(y-1);
          Gi[y-1].push_back(x-1);
    }

    used.resize(n+1);
    used.assign(n+1,0);

    where.resize(n+1);
    where.assign(n+1,-1);

    for(int i=0;i<n;i++)
        if(used[i]==false)
            DFP(i,Go);

    int coun=0;

    for(;discovered.size();discovered.pop_back())
      if(where[discovered.back()]==-1){
          DFM(discovered.back(),coun,Gi);
          coun++;
        }

    for(int i=0;i<n;i++)
        G[where[i]].push_back(i);

    vector<int>::iterator it;

    fout<<coun<<'\n';

    for(int i=0;i<coun;i++)
    {
      for(it=G[i].begin();it!=G[i].end();it++)
        fout<<*it+1<<' ';
      fout<<'\n';
    }



}