#include <fstream>
#include <vector>
#define NMAX 100004
using namespace std;
ifstream fin("ctc.in");
ofstream fout("ctc.out");
void citire();
void DFS(int x);
void DFST(int x);
void afisare();
int postsir[NMAX];
int fr[NMAX];
int cnt,nr;
int nrComponente;
int n,m;
vector <int> A[NMAX];
vector <int> AT[NMAX]; ///graful transpus
vector <int> afis[NMAX]; ///vectori in care vom retine componentele tari conexe
int main()
{int i;
    citire();
    for (i = 1; i <= n; i++)
        if (!fr[i])
    DFS(i);
    ///in fr vom schimba semnificatia nr
    ///vom avea 1 pentru nevizitat si 0 pentru vizitat
    ///luam vect postsir in ordine descrescatoare
    for (i = n; i > 0; i--)
        if (fr[postsir[i]])
    {
        nrComponente++;
        DFST(postsir[i]);
    }
    afisare();
    return 0;
}
void citire()
{int i,x,y;
    fin >> n >> m;
    for (i = 0; i < m; i++)
    {
        fin >> x >> y;
        A[x].push_back(y);
        ///A transpus
        AT[y].push_back(x);
    }
}
void DFS(int x)
{int j;
    fr[x] = 1;
    for (j = 0; j < A[x].size(); j++)
    if (!fr[A[x][j]])
        DFS(A[x][j]);
    postsir[++cnt] = x; /// retin mai intai toti vecinii si dupa numarul
}
void DFST(int x)
{int j;
    fr[x] = 0;
    afis[nrComponente].push_back(x);
    for (j = 0; j < AT[x].size(); j++)
    if (fr[AT[x][j]])
        DFST(AT[x][j]);
 
}
void afisare()
{int i,j;
    fout << nrComponente << '\n';
    for (i = 1; i <= nrComponente; i++)
    {
        for (j = 0; j < afis[i].size(); j++)
            fout << afis[i][j] << " ";
        fout << '\n';
    }
}