#include <fstream>
#include <vector>
#define NMAX 100002
using namespace std;

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

int n, m, nr, nrc;
vector <int> G[NMAX];
vector <int> GT[NMAX]; //graful transpus
vector <int> CTC[NMAX];
int postordine[NMAX];
bool uz[NMAX];
///ctc[i]=componenta tare conexa din care face parte vf i

void citire();
void DFS(int x);
void DFST(int x);
void afisare();
int main()
{
    int i;
    citire();
    ///etapa I
    DFS(1);
    for (i=1; i<=n; i++)
        if (!uz[i]) DFS(i);
    ///etapa II
    for (i=n; i>0; i--)
        if (uz[postordine[i]])
           {nrc++; DFST(postordine[i]);}
    afisare();
    return 0;
}

void citire()
{
    int i, x, y;
    fin>>n>>m;
    for (i=0; i<m; i++)
    {
        fin>>x>>y;
        G[x].push_back(y);
        GT[y].push_back(x); //in graful transpus
    }
}


void DFS(int x)
{
    int i;
    uz[x]=1;
    for (i=0; i<G[x].size(); i++) //nu imi fac probleme ca size se calculeaza constant!
        if (uz[G[x][i]]==0)
           DFS(G[x][i]);
    nr++;
    postordine[nr]=x;
}

void DFST(int x)
{
    int i;
    uz[x]=0;
    CTC[nrc].push_back(x);
    for (i=0; i<GT[x].size(); i++) //nu imi fac probleme ca size se calculeaza constant!
        if (uz[GT[x][i]]==1)
           DFST(GT[x][i]);
}

void afisare()
{
 int i, j;
 fout<<nrc<<'\n';
 for (i=1; i<=nrc; i++)
    {for (j=0; j<CTC[i].size(); j++)
         fout<<CTC[i][j]<<' ';
   fout<<'\n';}
}