#include <cstdio>
#include <vector>
#define nmax 100001
using namespace std;
FILE *fin=fopen("ctc.in", "r");
FILE *fout=fopen("ctc.out", "w");
vector<int> lista[nmax];
vector<int> listaT[nmax];
int n,m,k,nr;
int postord[nmax];
bool ver[nmax];
vector <int> ctc[nmax];

void citire();
void DFS(int vf);
void DFST(int vf);
void afisare();

int main()
{int i;
    citire();
    for (i=1; i<=n; i++)
      if (!ver[i])
         DFS(i);
    for (i=n; i>=1; i--)
      {
         if (ver[postord[i]])
            {k++;

             DFST(postord[i]);
            }
      }
    afisare();
    return 0;
}
void citire()
{
   int i,j,x,y;
   //fin>>n>>m;
   fscanf(fin, "%d%d", &n, &m);
   for (i=1; i<=m; i++)
      {
         //fin>>x>>y;
         fscanf(fin, "%d%d", &x, &y);
         lista[x].push_back(y);
         listaT[y].push_back(x);
      }
}
void DFS(int vf)
{int i;

   ver[vf]=1;
   for (i=0; i<lista[vf].size(); i++)
      {
         if (!ver[lista[vf][i]])
            DFS(lista[vf][i]);
      }
   postord[++nr]=vf;
}
void DFST(int vf)
{
   int i;
   ver[vf]=0;
   ctc[k].push_back(vf);
   for (i=0; i<listaT[vf].size(); i++)
      {
            if (ver[listaT[vf][i]])
               DFST(listaT[vf][i]);
      }
}
void afisare()
{int i,j;
   fprintf(fout, "%d\n", k);
   for (i=1; i<=k; i++)
      {for (j=0; j<ctc[i].size(); j++)
         fprintf(fout, "%d ", ctc[i][j]);
      fprintf(fout, "\n");
      }

}