#include <bits/stdc++.h>
using namespace std;
ifstream f("ctc.in");
ofstream g("ctc.out");

struct Nod
{
    int info;
    Nod *next;
};

Nod *lista[100001],*listaT[100001];
int n, m, nrctc, pred[100001], succ[100001];

void citire()
{
    f>>n>>m;
    int i, x, y;
    for (i = 1; i <= m; i++)
    {
        f>>x>>y;Nod *p=new Nod;p->next=lista[x];p->info=y;lista[x]=p;
        p=new Nod;p->next=listaT[y];p->info=x;listaT[y]=p;
    }
}

void df_succesor(int nod) //det multimea succesorilor lui nod
{
    succ[nod] = nrctc;
    for(Nod *p=lista[nod];p!=NULL;p=p->next)
          if (succ[p->info]==0) df_succesor(p->info);
}

void df_pred(int nod) //det multimea predecesorilor lui nod
{
    pred[nod] = nrctc;
    for(Nod *p=listaT[nod];p!=NULL;p=p->next)
          if (pred[p->info]==0) df_pred(p->info);
}

void intersectie()//pastreaza doar nodurile i care au pred[i]=succ[i]
{
   for(int i=1;i<=n;i++)
    if(pred[i]!=succ[i]) pred[i]=succ[i]=0;
}

int main()
{
    citire();int i,j;
    nrctc=1;
    for(i=1;i<=n;i++)
        if(succ[i]==0)
        {
             succ[i]=nrctc;
             df_succesor(i);df_pred(i);
             intersectie();
             nrctc++;
        }
    g<<nrctc-1<<"\n";
    for(i=1;i<nrctc;i++)
    {
        for(j=1;j<=n;j++)
            if(succ[j]==i)g<<j<<' ';
        g<<"\n";
    }
    f.close();g.close();return 0;
}