#include <fstream>
#include <vector>
#define NMAX 100002

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

int n, start, nr;
vector<int> G[NMAX];
vector<int> Gt[NMAX];
int postordine[NMAX];
vector<int> CTC[NMAX]; ///CTC[i] contine nodurile din componenta tare conexa i
bool viz[NMAX]; ///viz[x]==1 daca x a fost vizitat
void citire();
void dfs(int x);
void dfst(int x);
void afisare();

int main()
{
    int i;
    citire();
    for (i=1; i<=n; i++)
        if (!viz[i]) dfs(i);
    nr=0;
    for (i=n; i>=1; i--)
        if (viz[postordine[i]])
        {
            nr++;
            dfst(postordine[i]);
        }
    afisare();
    return 0;
}
void citire()
{
    int i, m, x, y;
    ///neorientat
    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;
    for (i=0; i<G[x].size(); i++)
        if (!viz[G[x][i]])
            dfs(G[x][i]);
    postordine[++nr]=x;
}
void dfst(int x)
{
    int i;
    viz[x]=0;
    CTC[nr].push_back(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';
    }
}