#include <fstream>
#define NMAX 100004

using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

struct nod{int nr;nod*urm;};
typedef nod*Lista;
Lista lis[NMAX],lisgt[NMAX];
int n,m,post[NMAX],uz[NMAX],np;

void bfs(int);
void dfs(int);
void inserare(Lista&,int);
void solve();
void read();
void write();

int main()
{
    read();
    solve();
    write();
    cin.close();cout.close();
    return 0;
}

void read()
{
    int i,x,y;
    cin>>n>>m;
    for (i=1;i<=n;i++) {lis[i]=NULL;lisgt[i]=NULL;uz[i]=1;}
    for (i=1;i<=m;i++)
    {
        cin>>x>>y;
        inserare(lis[x],y);
        inserare(lisgt[y],x);
    }
}

void inserare(Lista&prim,int nr)
{
    Lista aux;
    aux=new nod;
    aux->nr=nr;
    aux->urm=prim;
    prim=aux;
}

int nr;

void solve()
{
    int i;
    for (i=1;i<=n;i++)
        if (uz[i])
        dfs(i);
    for (i=n;i>=1;i--)
        if (!uz[post[i]])
        bfs(post[i]);
}

void dfs(int nod)
{
    Lista aux=lis[nod];
    uz[nod]=0;
    while (aux!=NULL)
    {
        if (uz[aux->nr])
            dfs(aux->nr);
        aux=aux->urm;
    }
    post[++np]=nod;
}

int que[NMAX];

void bfs(int nod)
{
    Lista aux;int p=1,u=1;
    nr++;
    que[1]=nod;uz[nod]=nr;
    while (p<=u)
    {
        aux=lisgt[que[p]]; p++;
        while (aux!=NULL)
        {
            if (!uz[aux->nr])
            {
                uz[aux->nr]=nr;
                que[++u]=aux->nr;
            }
            aux=aux->urm;
        }
    }
}

void write()
{
    int i,j;
    cout<<nr<<'\n';
    for (i=1;i<=nr;i++){
        for (j=1;j<=n;j++)
            if (uz[j]==i)
                cout<<j<<' ';
        cout<<'\n';
    }
}