#include <fstream>
#include <vector>
#define NMAX 100004
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
void citire();
void afisare();
void DFS(int x);
void DFST(int x);
int n,m;
///graful G reprezentat prin lsite de adiacenta
vector<int> G[NMAX];
///graful transpus GT
vector <int> GT[NMAX];
bool viz[NMAX];
int nr; ///nr de componente tare-conexe
vector <int> ctc[NMAX];
int postordine[NMAX];
int poz;
int main()
{int i,j;
   citire();
   ///parcurg prin DFS graful dat retinand varfurile in postordine
   for (i = 1; i <= n; i++)
    if(!viz[i])
   DFS(i);
   ///parcurg vect postordine de la dreapta la stanga si fac DFST
   for (i = n; i > 0; i--)
        if (viz[postordine[i]]) ///acest vf este nevizitat in GT
        {
            nr++;
            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);
    }
}
void DFS(int x)
{int i;
    viz[x] = 1;
    ///parcurg lista de adiacenta a lui x
    for (i = 0; i < G[x].size(); i++)
    if(!viz[G[x][i]])
        DFS(G[x][i]);
    postordine[++poz] = x;
}
void DFST(int x)
{
    int i;
    viz[x] = 0;
    ///retin acest varf in componenta conexa respectiva
    ctc[nr].push_back(x);
    ///parcurg lista de adiacenta a lui x
    for (i = 0; i < GT[x].size(); i++)
    if(viz[GT[x][i]])
        DFST(GT[x][i]);
}
void afisare()
{int i,j;
    fout << nr << '\n';
    for (i = 1; i <= nr; i++)
    {
        for (j = 0; j < ctc[i].size(); j++)
            fout << ctc[i][j] << " ";
        fout << '\n';
    }
}