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

ifstream fin("ctc.in");
ofstream fout("ctc.out");
const int NMax = 100005;
vector <int> G[NMax];
vector <int> GT[NMax];
vector <int> CTC[NMax];

int N,M,NrCTC;
int Use[NMax];

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[NrCTC].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 Solve()
{
  for(int i = 1; i <= N; ++i)
    {
      if(!Use[i])
        {
          NrCTC++;
          DFSP(i);
          DFSM(i);
          for(int i = 1; i <=N; ++i)
            if(Use[i] == 1)
              Use[i] = 0;
        }
    }
}

void Print()
{
  fout<<NrCTC<<"\n";
  for(int i = 1; i <= NrCTC; ++i)
    {
      for(int j = 0; j < (int)CTC[i].size(); ++j)
        fout<<CTC[i][j]<<" ";
      fout<<"\n";
    }
}

int main()
{
    Read();
    Solve();
    Print();
    return 0;
}