#include <iostream>
#include <fstream>
#include <vector>
#define N 100003
using namespace std;

ifstream f("ctc.in");
ofstream g("ctc.out");
vector < vector<int> > L(N);
vector < vector<int> > LT(N);
vector < vector<int> > TC(N); //retine componentele conexe

int n,m;
bool vizitat[N],vizitat2[N];
int stiva[N],vf;

void DF(int nod)
{
  int i;
  vizitat[nod]=1;
  for (i=0; i<L[nod].size();i++)
    if (!vizitat[L[nod][i]]) DF(L[nod][i]);
  vf++;stiva[vf]=nod;
}

void DF2(int nod,int k ) //pcompletam componenta tare conexa cun nr de ordine K
{
  int i;
  vizitat2[nod]=1; TC[k].push_back(nod);
  for (i=0; i<LT[nod].size();i++)
    if (!vizitat2[LT[nod][i]]) DF2(LT[nod][i],k);
}

 int main()
 {
   int i,k=0,x,y,j;
   f>>n>>m;
   for (i=1; i<=m; i++)
   {
     f>>x>>y;
     L[x].push_back(y);
     LT[y].push_back(x);
   }
// parcurgem in adncime graful
   for (i=1; i<=n; i++)
   {
       if(!vizitat[i]) DF(i);
   }

// parcurgem in adncime graful transpus in ordinea in care
//vom scoate din stiva nodurile
   while(vf)
   {
       if(!vizitat2[stiva[vf]])
       {
         k++;
         DF2(stiva[vf],k);
       }
       vf--;
   }

   g<<k<<'\n';
   j=1;
   for(i=1;i<=k;i++)
   {
       for (j=0; j<TC[i].size();j++) g<<TC[i][j]<<" ";
       g<<'\n';
   }
   f.close();g.close();
   return 0;
}