#include <fstream>
#include <vector>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");
#define nmax 100003
int n,m,x,cnt,postordine[nmax],nr,y;
vector < int > matrice[nmax];
vector < int > matrice_transpusa[nmax];
vector < int > matrice_afisare[nmax];
bool viz[nmax];
void DFS(int nod)
{
    viz[nod]=1;
    for(vector < int > ::iterator it=matrice[nod].begin(); it!=matrice[nod].end(); it++)
        if(!viz[*it]) DFS(*it);
    postordine[++nr]=nod;
}
void DFS2(int nod)
{
    matrice_afisare[cnt].push_back(nod);
    viz[nod]=0;
    for(vector < int > ::iterator it=matrice_transpusa[nod].begin(); it!=matrice_transpusa[nod].end(); it++)
        if(viz[*it]) DFS2(*it);
}
void Afisare()
{
    for(int i=1; i<=cnt; i++)
    {
        for(vector < int > ::iterator it=matrice_afisare[i].begin();it!=matrice_afisare[i].end();it++)
            g<<*it<<" ";
        g<<'\n';
    }
}
int main()
{
    f>>n>>m;
    for(int i=1; i<=m; i++)
    {
            f>>x>>y;
            matrice[x].push_back(y);
            matrice_transpusa[y].push_back(x);
    }
    for(int i=1; i<=n; i++)
        if(!viz[i]) DFS(i);
    for(int i=n; i>=1; i--)
        if(viz[postordine[i]])
        {
            cnt++;
            DFS2(postordine[i]);
        }
        g<<cnt<<'\n';
    Afisare();
    return 0;
}