#include <fstream>
#include <vector>
using namespace std;

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

const int NMax = 100005;
int N,M,Use[NMax];
vector <int> G[NMax];
vector <int> GT[NMax];
vector <int> CTC[NMax];
int k;

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(int i = 0; i < (int)G[Nod].size(); ++i)
    {
      int Vecin = G[Nod][i];
      if(Use[Vecin] == 0)
        {
          DFSP(Vecin);
        }
    }
}
void DFSM(int Nod)
{
  Use[Nod] = 2;

  CTC[k].push_back(Nod);

  for(int i = 0; i < (int)GT[Nod].size(); ++i)
    {
      int Vecin = GT[Nod][i];
      if(Use[Vecin] == 1)
        {
          DFSM(Vecin);
        }
    }
}
void Print()
{
  fout<<k<<"\n";
  for(int i = 1; i <= k; ++i)
    {
      for(int j  = 0; j < (int)CTC[i].size(); ++j)
        fout<<CTC[i][j]<<" ";
      fout<<"\n";
    }
  fout<<"\n";
}
int main()
{
    Read();
    for(int i = 1; i <= N; ++i)
      if(Use[i] == 0 )
        {
          k++;
          DFSP(i);
          DFSM(i);
          for(int j = 1; j <= N; ++j)
            if(Use[j] == 1)
              Use[j] = 0;
        }
    Print();
    return 0;
}